1<!DOCTYPE html> 2<html lang="en"> 3<head> 4 <meta charset="utf-8"> 5 <meta name="viewport" content="width=device-width"> 6 <meta name="nodejs.org:node-version" content="v18.18.2"> 7 <title>DNS | Node.js v18.18.2 Documentation</title> 8 <link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Lato:400,700,400italic&display=fallback"> 9 <link rel="stylesheet" href="assets/style.css"> 10 <link rel="stylesheet" href="assets/hljs.css"> 11 <link rel="canonical" href="https://nodejs.org/api/dns.html"> 12 <script async defer src="assets/api.js" type="text/javascript"></script> 13 14</head> 15<body class="alt apidoc" id="api-section-dns"> 16 <div id="content" class="clearfix"> 17 <div id="column2" class="interior"> 18 <div id="intro" class="interior"> 19 <a href="/" title="Go back to the home page"> 20 Node.js 21 </a> 22 </div> 23 <ul> 24<li><a href="documentation.html" class="nav-documentation">About this documentation</a></li> 25<li><a href="synopsis.html" 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class="picker-header"> 117 <a href="#"> 118 <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 119 Table of contents 120 </a> 121 122 <div class="picker"><div class="toc"><ul> 123<li><span class="stability_2"><a href="#dns">DNS</a></span> 124<ul> 125<li><a href="#class-dnsresolver">Class: <code>dns.Resolver</code></a> 126<ul> 127<li><a href="#resolveroptions"><code>Resolver([options])</code></a></li> 128<li><a href="#resolvercancel"><code>resolver.cancel()</code></a></li> 129<li><a href="#resolversetlocaladdressipv4-ipv6"><code>resolver.setLocalAddress([ipv4][, ipv6])</code></a></li> 130</ul> 131</li> 132<li><a href="#dnsgetservers"><code>dns.getServers()</code></a></li> 133<li><a href="#dnslookuphostname-options-callback"><code>dns.lookup(hostname[, options], callback)</code></a> 134<ul> 135<li><a href="#supported-getaddrinfo-flags">Supported getaddrinfo flags</a></li> 136</ul> 137</li> 138<li><a href="#dnslookupserviceaddress-port-callback"><code>dns.lookupService(address, port, callback)</code></a></li> 139<li><a href="#dnsresolvehostname-rrtype-callback"><code>dns.resolve(hostname[, rrtype], callback)</code></a></li> 140<li><a href="#dnsresolve4hostname-options-callback"><code>dns.resolve4(hostname[, options], callback)</code></a></li> 141<li><a href="#dnsresolve6hostname-options-callback"><code>dns.resolve6(hostname[, options], callback)</code></a></li> 142<li><a href="#dnsresolveanyhostname-callback"><code>dns.resolveAny(hostname, callback)</code></a></li> 143<li><a href="#dnsresolvecnamehostname-callback"><code>dns.resolveCname(hostname, callback)</code></a></li> 144<li><a href="#dnsresolvecaahostname-callback"><code>dns.resolveCaa(hostname, callback)</code></a></li> 145<li><a href="#dnsresolvemxhostname-callback"><code>dns.resolveMx(hostname, callback)</code></a></li> 146<li><a href="#dnsresolvenaptrhostname-callback"><code>dns.resolveNaptr(hostname, callback)</code></a></li> 147<li><a href="#dnsresolvenshostname-callback"><code>dns.resolveNs(hostname, callback)</code></a></li> 148<li><a href="#dnsresolveptrhostname-callback"><code>dns.resolvePtr(hostname, callback)</code></a></li> 149<li><a href="#dnsresolvesoahostname-callback"><code>dns.resolveSoa(hostname, callback)</code></a></li> 150<li><a href="#dnsresolvesrvhostname-callback"><code>dns.resolveSrv(hostname, callback)</code></a></li> 151<li><a href="#dnsresolvetxthostname-callback"><code>dns.resolveTxt(hostname, callback)</code></a></li> 152<li><a href="#dnsreverseip-callback"><code>dns.reverse(ip, callback)</code></a></li> 153<li><a href="#dnssetdefaultresultorderorder"><code>dns.setDefaultResultOrder(order)</code></a></li> 154<li><a href="#dnsgetdefaultresultorder"><code>dns.getDefaultResultOrder()</code></a></li> 155<li><a href="#dnssetserversservers"><code>dns.setServers(servers)</code></a></li> 156<li><a href="#dns-promises-api">DNS promises API</a> 157<ul> 158<li><a href="#class-dnspromisesresolver">Class: <code>dnsPromises.Resolver</code></a></li> 159<li><a href="#resolvercancel_1"><code>resolver.cancel()</code></a></li> 160<li><a href="#dnspromisesgetservers"><code>dnsPromises.getServers()</code></a></li> 161<li><a href="#dnspromiseslookuphostname-options"><code>dnsPromises.lookup(hostname[, options])</code></a></li> 162<li><a href="#dnspromiseslookupserviceaddress-port"><code>dnsPromises.lookupService(address, port)</code></a></li> 163<li><a href="#dnspromisesresolvehostname-rrtype"><code>dnsPromises.resolve(hostname[, rrtype])</code></a></li> 164<li><a href="#dnspromisesresolve4hostname-options"><code>dnsPromises.resolve4(hostname[, options])</code></a></li> 165<li><a href="#dnspromisesresolve6hostname-options"><code>dnsPromises.resolve6(hostname[, options])</code></a></li> 166<li><a href="#dnspromisesresolveanyhostname"><code>dnsPromises.resolveAny(hostname)</code></a></li> 167<li><a href="#dnspromisesresolvecaahostname"><code>dnsPromises.resolveCaa(hostname)</code></a></li> 168<li><a href="#dnspromisesresolvecnamehostname"><code>dnsPromises.resolveCname(hostname)</code></a></li> 169<li><a href="#dnspromisesresolvemxhostname"><code>dnsPromises.resolveMx(hostname)</code></a></li> 170<li><a href="#dnspromisesresolvenaptrhostname"><code>dnsPromises.resolveNaptr(hostname)</code></a></li> 171<li><a href="#dnspromisesresolvenshostname"><code>dnsPromises.resolveNs(hostname)</code></a></li> 172<li><a href="#dnspromisesresolveptrhostname"><code>dnsPromises.resolvePtr(hostname)</code></a></li> 173<li><a href="#dnspromisesresolvesoahostname"><code>dnsPromises.resolveSoa(hostname)</code></a></li> 174<li><a href="#dnspromisesresolvesrvhostname"><code>dnsPromises.resolveSrv(hostname)</code></a></li> 175<li><a href="#dnspromisesresolvetxthostname"><code>dnsPromises.resolveTxt(hostname)</code></a></li> 176<li><a href="#dnspromisesreverseip"><code>dnsPromises.reverse(ip)</code></a></li> 177<li><a href="#dnspromisessetdefaultresultorderorder"><code>dnsPromises.setDefaultResultOrder(order)</code></a></li> 178<li><a href="#dnspromisesgetdefaultresultorder"><code>dnsPromises.getDefaultResultOrder()</code></a></li> 179<li><a href="#dnspromisessetserversservers"><code>dnsPromises.setServers(servers)</code></a></li> 180</ul> 181</li> 182<li><a href="#error-codes">Error codes</a></li> 183<li><a href="#implementation-considerations">Implementation considerations</a> 184<ul> 185<li><a href="#dnslookup"><code>dns.lookup()</code></a></li> 186<li><a href="#dnsresolve-dnsresolve-and-dnsreverse"><code>dns.resolve()</code>, <code>dns.resolve*()</code>, and <code>dns.reverse()</code></a></li> 187</ul> 188</li> 189</ul> 190</li> 191</ul></div></div> 192 </li> 193 194 195 <li class="picker-header"> 196 <a href="#"> 197 <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 198 Index 199 </a> 200 201 <div class="picker"><ul> 202<li><a href="documentation.html" class="nav-documentation">About this documentation</a></li> 203<li><a href="synopsis.html" class="nav-synopsis">Usage and example</a></li> 204 205 <li> 206 <a href="index.html">Index</a> 207 </li> 208 </ul> 209 210<hr class="line"> 211<ul> 212<li><a href="assert.html" class="nav-assert">Assertion testing</a></li> 213<li><a href="async_context.html" class="nav-async_context">Asynchronous context tracking</a></li> 214<li><a href="async_hooks.html" class="nav-async_hooks">Async hooks</a></li> 215<li><a href="buffer.html" class="nav-buffer">Buffer</a></li> 216<li><a href="addons.html" class="nav-addons">C++ addons</a></li> 217<li><a href="n-api.html" class="nav-n-api">C/C++ addons with Node-API</a></li> 218<li><a href="embedding.html" class="nav-embedding">C++ embedder API</a></li> 219<li><a href="child_process.html" class="nav-child_process">Child processes</a></li> 220<li><a href="cluster.html" class="nav-cluster">Cluster</a></li> 221<li><a href="cli.html" class="nav-cli">Command-line options</a></li> 222<li><a href="console.html" class="nav-console">Console</a></li> 223<li><a href="corepack.html" class="nav-corepack">Corepack</a></li> 224<li><a href="crypto.html" class="nav-crypto">Crypto</a></li> 225<li><a href="debugger.html" class="nav-debugger">Debugger</a></li> 226<li><a href="deprecations.html" class="nav-deprecations">Deprecated APIs</a></li> 227<li><a href="diagnostics_channel.html" class="nav-diagnostics_channel">Diagnostics Channel</a></li> 228<li><a href="dns.html" class="nav-dns active">DNS</a></li> 229<li><a href="domain.html" class="nav-domain">Domain</a></li> 230<li><a href="errors.html" class="nav-errors">Errors</a></li> 231<li><a href="events.html" class="nav-events">Events</a></li> 232<li><a href="fs.html" class="nav-fs">File system</a></li> 233<li><a href="globals.html" class="nav-globals">Globals</a></li> 234<li><a href="http.html" 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class="nav-process">Process</a></li> 249<li><a href="punycode.html" class="nav-punycode">Punycode</a></li> 250<li><a href="querystring.html" class="nav-querystring">Query strings</a></li> 251<li><a href="readline.html" class="nav-readline">Readline</a></li> 252<li><a href="repl.html" class="nav-repl">REPL</a></li> 253<li><a href="report.html" class="nav-report">Report</a></li> 254<li><a href="single-executable-applications.html" class="nav-single-executable-applications">Single executable applications</a></li> 255<li><a href="stream.html" class="nav-stream">Stream</a></li> 256<li><a href="string_decoder.html" class="nav-string_decoder">String decoder</a></li> 257<li><a href="test.html" class="nav-test">Test runner</a></li> 258<li><a href="timers.html" class="nav-timers">Timers</a></li> 259<li><a href="tls.html" class="nav-tls">TLS/SSL</a></li> 260<li><a href="tracing.html" class="nav-tracing">Trace events</a></li> 261<li><a href="tty.html" class="nav-tty">TTY</a></li> 262<li><a href="dgram.html" class="nav-dgram">UDP/datagram</a></li> 263<li><a href="url.html" class="nav-url">URL</a></li> 264<li><a href="util.html" class="nav-util">Utilities</a></li> 265<li><a href="v8.html" class="nav-v8">V8</a></li> 266<li><a href="vm.html" class="nav-vm">VM</a></li> 267<li><a href="wasi.html" class="nav-wasi">WASI</a></li> 268<li><a href="webcrypto.html" class="nav-webcrypto">Web Crypto API</a></li> 269<li><a href="webstreams.html" class="nav-webstreams">Web Streams API</a></li> 270<li><a href="worker_threads.html" class="nav-worker_threads">Worker threads</a></li> 271<li><a href="zlib.html" class="nav-zlib">Zlib</a></li> 272</ul> 273<hr class="line"> 274<ul> 275<li><a href="https://github.com/nodejs/node" class="nav-https-github-com-nodejs-node">Code repository and issue tracker</a></li> 276</ul></div> 277 </li> 278 279 280 <li class="picker-header"> 281 <a href="#"> 282 <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 283 Other versions 284 </a> 285 <div class="picker"><ol id="alt-docs"><li><a href="https://nodejs.org/docs/latest-v20.x/api/dns.html">20.x</a></li> 286<li><a href="https://nodejs.org/docs/latest-v19.x/api/dns.html">19.x</a></li> 287<li><a href="https://nodejs.org/docs/latest-v18.x/api/dns.html">18.x <b>LTS</b></a></li> 288<li><a href="https://nodejs.org/docs/latest-v17.x/api/dns.html">17.x</a></li> 289<li><a href="https://nodejs.org/docs/latest-v16.x/api/dns.html">16.x</a></li> 290<li><a href="https://nodejs.org/docs/latest-v15.x/api/dns.html">15.x</a></li> 291<li><a href="https://nodejs.org/docs/latest-v14.x/api/dns.html">14.x</a></li> 292<li><a href="https://nodejs.org/docs/latest-v13.x/api/dns.html">13.x</a></li> 293<li><a href="https://nodejs.org/docs/latest-v12.x/api/dns.html">12.x</a></li> 294<li><a href="https://nodejs.org/docs/latest-v11.x/api/dns.html">11.x</a></li> 295<li><a href="https://nodejs.org/docs/latest-v10.x/api/dns.html">10.x</a></li> 296<li><a href="https://nodejs.org/docs/latest-v9.x/api/dns.html">9.x</a></li> 297<li><a href="https://nodejs.org/docs/latest-v8.x/api/dns.html">8.x</a></li> 298<li><a href="https://nodejs.org/docs/latest-v7.x/api/dns.html">7.x</a></li> 299<li><a href="https://nodejs.org/docs/latest-v6.x/api/dns.html">6.x</a></li> 300<li><a href="https://nodejs.org/docs/latest-v5.x/api/dns.html">5.x</a></li> 301<li><a href="https://nodejs.org/docs/latest-v4.x/api/dns.html">4.x</a></li> 302<li><a href="https://nodejs.org/docs/latest-v0.12.x/api/dns.html">0.12.x</a></li> 303<li><a href="https://nodejs.org/docs/latest-v0.10.x/api/dns.html">0.10.x</a></li></ol></div> 304 </li> 305 306 <li class="picker-header"> 307 <a href="#"> 308 <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 309 Options 310 </a> 311 312 <div class="picker"> 313 <ul> 314 <li> 315 <a href="all.html">View on single page</a> 316 </li> 317 <li> 318 <a href="dns.json">View as JSON</a> 319 </li> 320 <li class="edit_on_github"><a href="https://github.com/nodejs/node/edit/main/doc/api/dns.md">Edit on GitHub</a></li> 321 </ul> 322 </div> 323 </li> 324 </ul> 325 </div> 326 <hr> 327 </header> 328 329 <details id="toc" open><summary>Table of contents</summary><ul> 330<li><span class="stability_2"><a href="#dns">DNS</a></span> 331<ul> 332<li><a href="#class-dnsresolver">Class: <code>dns.Resolver</code></a> 333<ul> 334<li><a href="#resolveroptions"><code>Resolver([options])</code></a></li> 335<li><a href="#resolvercancel"><code>resolver.cancel()</code></a></li> 336<li><a href="#resolversetlocaladdressipv4-ipv6"><code>resolver.setLocalAddress([ipv4][, ipv6])</code></a></li> 337</ul> 338</li> 339<li><a href="#dnsgetservers"><code>dns.getServers()</code></a></li> 340<li><a href="#dnslookuphostname-options-callback"><code>dns.lookup(hostname[, options], callback)</code></a> 341<ul> 342<li><a href="#supported-getaddrinfo-flags">Supported getaddrinfo flags</a></li> 343</ul> 344</li> 345<li><a href="#dnslookupserviceaddress-port-callback"><code>dns.lookupService(address, port, callback)</code></a></li> 346<li><a href="#dnsresolvehostname-rrtype-callback"><code>dns.resolve(hostname[, rrtype], callback)</code></a></li> 347<li><a href="#dnsresolve4hostname-options-callback"><code>dns.resolve4(hostname[, options], callback)</code></a></li> 348<li><a href="#dnsresolve6hostname-options-callback"><code>dns.resolve6(hostname[, options], callback)</code></a></li> 349<li><a href="#dnsresolveanyhostname-callback"><code>dns.resolveAny(hostname, callback)</code></a></li> 350<li><a href="#dnsresolvecnamehostname-callback"><code>dns.resolveCname(hostname, callback)</code></a></li> 351<li><a href="#dnsresolvecaahostname-callback"><code>dns.resolveCaa(hostname, callback)</code></a></li> 352<li><a href="#dnsresolvemxhostname-callback"><code>dns.resolveMx(hostname, callback)</code></a></li> 353<li><a href="#dnsresolvenaptrhostname-callback"><code>dns.resolveNaptr(hostname, callback)</code></a></li> 354<li><a href="#dnsresolvenshostname-callback"><code>dns.resolveNs(hostname, callback)</code></a></li> 355<li><a href="#dnsresolveptrhostname-callback"><code>dns.resolvePtr(hostname, callback)</code></a></li> 356<li><a href="#dnsresolvesoahostname-callback"><code>dns.resolveSoa(hostname, callback)</code></a></li> 357<li><a href="#dnsresolvesrvhostname-callback"><code>dns.resolveSrv(hostname, callback)</code></a></li> 358<li><a href="#dnsresolvetxthostname-callback"><code>dns.resolveTxt(hostname, callback)</code></a></li> 359<li><a href="#dnsreverseip-callback"><code>dns.reverse(ip, callback)</code></a></li> 360<li><a href="#dnssetdefaultresultorderorder"><code>dns.setDefaultResultOrder(order)</code></a></li> 361<li><a href="#dnsgetdefaultresultorder"><code>dns.getDefaultResultOrder()</code></a></li> 362<li><a href="#dnssetserversservers"><code>dns.setServers(servers)</code></a></li> 363<li><a href="#dns-promises-api">DNS promises API</a> 364<ul> 365<li><a href="#class-dnspromisesresolver">Class: <code>dnsPromises.Resolver</code></a></li> 366<li><a href="#resolvercancel_1"><code>resolver.cancel()</code></a></li> 367<li><a href="#dnspromisesgetservers"><code>dnsPromises.getServers()</code></a></li> 368<li><a href="#dnspromiseslookuphostname-options"><code>dnsPromises.lookup(hostname[, options])</code></a></li> 369<li><a href="#dnspromiseslookupserviceaddress-port"><code>dnsPromises.lookupService(address, port)</code></a></li> 370<li><a href="#dnspromisesresolvehostname-rrtype"><code>dnsPromises.resolve(hostname[, rrtype])</code></a></li> 371<li><a href="#dnspromisesresolve4hostname-options"><code>dnsPromises.resolve4(hostname[, options])</code></a></li> 372<li><a href="#dnspromisesresolve6hostname-options"><code>dnsPromises.resolve6(hostname[, options])</code></a></li> 373<li><a href="#dnspromisesresolveanyhostname"><code>dnsPromises.resolveAny(hostname)</code></a></li> 374<li><a href="#dnspromisesresolvecaahostname"><code>dnsPromises.resolveCaa(hostname)</code></a></li> 375<li><a href="#dnspromisesresolvecnamehostname"><code>dnsPromises.resolveCname(hostname)</code></a></li> 376<li><a href="#dnspromisesresolvemxhostname"><code>dnsPromises.resolveMx(hostname)</code></a></li> 377<li><a href="#dnspromisesresolvenaptrhostname"><code>dnsPromises.resolveNaptr(hostname)</code></a></li> 378<li><a href="#dnspromisesresolvenshostname"><code>dnsPromises.resolveNs(hostname)</code></a></li> 379<li><a href="#dnspromisesresolveptrhostname"><code>dnsPromises.resolvePtr(hostname)</code></a></li> 380<li><a href="#dnspromisesresolvesoahostname"><code>dnsPromises.resolveSoa(hostname)</code></a></li> 381<li><a href="#dnspromisesresolvesrvhostname"><code>dnsPromises.resolveSrv(hostname)</code></a></li> 382<li><a href="#dnspromisesresolvetxthostname"><code>dnsPromises.resolveTxt(hostname)</code></a></li> 383<li><a href="#dnspromisesreverseip"><code>dnsPromises.reverse(ip)</code></a></li> 384<li><a href="#dnspromisessetdefaultresultorderorder"><code>dnsPromises.setDefaultResultOrder(order)</code></a></li> 385<li><a href="#dnspromisesgetdefaultresultorder"><code>dnsPromises.getDefaultResultOrder()</code></a></li> 386<li><a href="#dnspromisessetserversservers"><code>dnsPromises.setServers(servers)</code></a></li> 387</ul> 388</li> 389<li><a href="#error-codes">Error codes</a></li> 390<li><a href="#implementation-considerations">Implementation considerations</a> 391<ul> 392<li><a href="#dnslookup"><code>dns.lookup()</code></a></li> 393<li><a href="#dnsresolve-dnsresolve-and-dnsreverse"><code>dns.resolve()</code>, <code>dns.resolve*()</code>, and <code>dns.reverse()</code></a></li> 394</ul> 395</li> 396</ul> 397</li> 398</ul></details> 399 400 <div id="apicontent"> 401 <h2>DNS<span><a class="mark" href="#dns" id="dns">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns"></a></h2> 402 403<p></p><div class="api_stability api_stability_2"><a href="documentation.html#stability-index">Stability: 2</a> - Stable</div><p></p> 404<p><strong>Source Code:</strong> <a href="https://github.com/nodejs/node/blob/v18.18.2/lib/dns.js">lib/dns.js</a></p> 405<p>The <code>node:dns</code> module enables name resolution. For example, use it to look up IP 406addresses of host names.</p> 407<p>Although named for the <a href="https://en.wikipedia.org/wiki/Domain_Name_System">Domain Name System (DNS)</a>, it does not always use the 408DNS protocol for lookups. <a href="#dnslookuphostname-options-callback"><code>dns.lookup()</code></a> uses the operating system 409facilities to perform name resolution. It may not need to perform any network 410communication. To perform name resolution the way other applications on the same 411system do, use <a href="#dnslookuphostname-options-callback"><code>dns.lookup()</code></a>.</p> 412<pre><code class="language-js"><span class="hljs-keyword">const</span> dns = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:dns'</span>); 413 414dns.<span class="hljs-title function_">lookup</span>(<span class="hljs-string">'example.org'</span>, <span class="hljs-function">(<span class="hljs-params">err, address, family</span>) =></span> { 415 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'address: %j family: IPv%s'</span>, address, family); 416}); 417<span class="hljs-comment">// address: "93.184.216.34" family: IPv4</span></code> <button class="copy-button">copy</button></pre> 418<p>All other functions in the <code>node:dns</code> module connect to an actual DNS server to 419perform name resolution. They will always use the network to perform DNS 420queries. These functions do not use the same set of configuration files used by 421<a href="#dnslookuphostname-options-callback"><code>dns.lookup()</code></a> (e.g. <code>/etc/hosts</code>). Use these functions to always perform 422DNS queries, bypassing other name-resolution facilities.</p> 423<pre><code class="language-js"><span class="hljs-keyword">const</span> dns = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:dns'</span>); 424 425dns.<span class="hljs-title function_">resolve4</span>(<span class="hljs-string">'archive.org'</span>, <span class="hljs-function">(<span class="hljs-params">err, addresses</span>) =></span> { 426 <span class="hljs-keyword">if</span> (err) <span class="hljs-keyword">throw</span> err; 427 428 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`addresses: <span class="hljs-subst">${<span class="hljs-built_in">JSON</span>.stringify(addresses)}</span>`</span>); 429 430 addresses.<span class="hljs-title function_">forEach</span>(<span class="hljs-function">(<span class="hljs-params">a</span>) =></span> { 431 dns.<span class="hljs-title function_">reverse</span>(a, <span class="hljs-function">(<span class="hljs-params">err, hostnames</span>) =></span> { 432 <span class="hljs-keyword">if</span> (err) { 433 <span class="hljs-keyword">throw</span> err; 434 } 435 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`reverse for <span class="hljs-subst">${a}</span>: <span class="hljs-subst">${<span class="hljs-built_in">JSON</span>.stringify(hostnames)}</span>`</span>); 436 }); 437 }); 438});</code> <button class="copy-button">copy</button></pre> 439<p>See the <a href="#implementation-considerations">Implementation considerations section</a> for more information.</p> 440<section><h3>Class: <code>dns.Resolver</code><span><a class="mark" href="#class-dnsresolver" id="class-dnsresolver">#</a></span><a aria-hidden="true" class="legacy" id="dns_class_dns_resolver"></a></h3> 441<div class="api_metadata"> 442<span>Added in: v8.3.0</span> 443</div> 444<p>An independent resolver for DNS requests.</p> 445<p>Creating a new resolver uses the default server settings. Setting 446the servers used for a resolver using 447<a href="#dnssetserversservers"><code>resolver.setServers()</code></a> does not affect 448other resolvers:</p> 449<pre><code class="language-js"><span class="hljs-keyword">const</span> { <span class="hljs-title class_">Resolver</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:dns'</span>); 450<span class="hljs-keyword">const</span> resolver = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Resolver</span>(); 451resolver.<span class="hljs-title function_">setServers</span>([<span class="hljs-string">'4.4.4.4'</span>]); 452 453<span class="hljs-comment">// This request will use the server at 4.4.4.4, independent of global settings.</span> 454resolver.<span class="hljs-title function_">resolve4</span>(<span class="hljs-string">'example.org'</span>, <span class="hljs-function">(<span class="hljs-params">err, addresses</span>) =></span> { 455 <span class="hljs-comment">// ...</span> 456});</code> <button class="copy-button">copy</button></pre> 457<p>The following methods from the <code>node:dns</code> module are available:</p> 458<ul> 459<li><a href="#dnsgetservers"><code>resolver.getServers()</code></a></li> 460<li><a href="#dnsresolvehostname-rrtype-callback"><code>resolver.resolve()</code></a></li> 461<li><a href="#dnsresolve4hostname-options-callback"><code>resolver.resolve4()</code></a></li> 462<li><a href="#dnsresolve6hostname-options-callback"><code>resolver.resolve6()</code></a></li> 463<li><a href="#dnsresolveanyhostname-callback"><code>resolver.resolveAny()</code></a></li> 464<li><a href="#dnsresolvecaahostname-callback"><code>resolver.resolveCaa()</code></a></li> 465<li><a href="#dnsresolvecnamehostname-callback"><code>resolver.resolveCname()</code></a></li> 466<li><a href="#dnsresolvemxhostname-callback"><code>resolver.resolveMx()</code></a></li> 467<li><a href="#dnsresolvenaptrhostname-callback"><code>resolver.resolveNaptr()</code></a></li> 468<li><a href="#dnsresolvenshostname-callback"><code>resolver.resolveNs()</code></a></li> 469<li><a href="#dnsresolveptrhostname-callback"><code>resolver.resolvePtr()</code></a></li> 470<li><a href="#dnsresolvesoahostname-callback"><code>resolver.resolveSoa()</code></a></li> 471<li><a href="#dnsresolvesrvhostname-callback"><code>resolver.resolveSrv()</code></a></li> 472<li><a href="#dnsresolvetxthostname-callback"><code>resolver.resolveTxt()</code></a></li> 473<li><a href="#dnsreverseip-callback"><code>resolver.reverse()</code></a></li> 474<li><a href="#dnssetserversservers"><code>resolver.setServers()</code></a></li> 475</ul> 476<h4><code>Resolver([options])</code><span><a class="mark" href="#resolveroptions" id="resolveroptions">#</a></span><a aria-hidden="true" class="legacy" id="dns_resolver_options"></a></h4> 477<div class="api_metadata"> 478<details class="changelog"><summary>History</summary> 479<table> 480<tbody><tr><th>Version</th><th>Changes</th></tr> 481<tr><td>v16.7.0, v14.18.0</td> 482<td><p>The <code>options</code> object now accepts a <code>tries</code> option.</p></td></tr> 483<tr><td>v12.18.3</td> 484<td><p>The constructor now accepts an <code>options</code> object. The single supported option is <code>timeout</code>.</p></td></tr> 485<tr><td>v8.3.0</td> 486<td><p><span>Added in: v8.3.0</span></p></td></tr> 487</tbody></table> 488</details> 489</div> 490<p>Create a new resolver.</p> 491<ul> 492<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 493<ul> 494<li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Query timeout in milliseconds, or <code>-1</code> to use the 495default timeout.</li> 496<li><code>tries</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The number of tries the resolver will try contacting 497each name server before giving up. <strong>Default:</strong> <code>4</code></li> 498</ul> 499</li> 500</ul> 501<h4><code>resolver.cancel()</code><span><a class="mark" href="#resolvercancel" id="resolvercancel">#</a></span><a aria-hidden="true" class="legacy" id="dns_resolver_cancel"></a></h4> 502<div class="api_metadata"> 503<span>Added in: v8.3.0</span> 504</div> 505<p>Cancel all outstanding DNS queries made by this resolver. The corresponding 506callbacks will be called with an error with code <code>ECANCELLED</code>.</p> 507<h4><code>resolver.setLocalAddress([ipv4][, ipv6])</code><span><a class="mark" href="#resolversetlocaladdressipv4-ipv6" id="resolversetlocaladdressipv4-ipv6">#</a></span><a aria-hidden="true" class="legacy" id="dns_resolver_setlocaladdress_ipv4_ipv6"></a></h4> 508<div class="api_metadata"> 509<span>Added in: v15.1.0, v14.17.0</span> 510</div> 511<ul> 512<li><code>ipv4</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> A string representation of an IPv4 address. 513<strong>Default:</strong> <code>'0.0.0.0'</code></li> 514<li><code>ipv6</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> A string representation of an IPv6 address. 515<strong>Default:</strong> <code>'::0'</code></li> 516</ul> 517<p>The resolver instance will send its requests from the specified IP address. 518This allows programs to specify outbound interfaces when used on multi-homed 519systems.</p> 520<p>If a v4 or v6 address is not specified, it is set to the default and the 521operating system will choose a local address automatically.</p> 522<p>The resolver will use the v4 local address when making requests to IPv4 DNS 523servers, and the v6 local address when making requests to IPv6 DNS servers. 524The <code>rrtype</code> of resolution requests has no impact on the local address used.</p> 525</section><section><h3><code>dns.getServers()</code><span><a class="mark" href="#dnsgetservers" id="dnsgetservers">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_getservers"></a></h3> 526<div class="api_metadata"> 527<span>Added in: v0.11.3</span> 528</div> 529<ul> 530<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li> 531</ul> 532<p>Returns an array of IP address strings, formatted according to <a href="https://tools.ietf.org/html/rfc5952#section-6">RFC 5952</a>, 533that are currently configured for DNS resolution. A string will include a port 534section if a custom port is used.</p> 535<!-- eslint-disable semi--> 536<pre><code class="language-js">[ 537 <span class="hljs-string">'4.4.4.4'</span>, 538 <span class="hljs-string">'2001:4860:4860::8888'</span>, 539 <span class="hljs-string">'4.4.4.4:1053'</span>, 540 <span class="hljs-string">'[2001:4860:4860::8888]:1053'</span>, 541]</code> <button class="copy-button">copy</button></pre> 542</section><section><h3><code>dns.lookup(hostname[, options], callback)</code><span><a class="mark" href="#dnslookuphostname-options-callback" id="dnslookuphostname-options-callback">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_lookup_hostname_options_callback"></a></h3> 543<div class="api_metadata"> 544<details class="changelog"><summary>History</summary> 545<table> 546<tbody><tr><th>Version</th><th>Changes</th></tr> 547<tr><td>v18.4.0</td> 548<td><p>For compatibility with <code>node:net</code>, when passing an option object the <code>family</code> option can be the string <code>'IPv4'</code> or the string <code>'IPv6'</code>.</p></td></tr> 549<tr><td>v18.0.0</td> 550<td><p>Passing an invalid callback to the <code>callback</code> argument now throws <code>ERR_INVALID_ARG_TYPE</code> instead of <code>ERR_INVALID_CALLBACK</code>.</p></td></tr> 551<tr><td>v17.0.0</td> 552<td><p>The <code>verbatim</code> options defaults to <code>true</code> now.</p></td></tr> 553<tr><td>v8.5.0</td> 554<td><p>The <code>verbatim</code> option is supported now.</p></td></tr> 555<tr><td>v1.2.0</td> 556<td><p>The <code>all</code> option is supported now.</p></td></tr> 557<tr><td>v0.1.90</td> 558<td><p><span>Added in: v0.1.90</span></p></td></tr> 559</tbody></table> 560</details> 561</div> 562<ul> 563<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 564<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 565<ul> 566<li><code>family</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The record family. Must be <code>4</code>, <code>6</code>, or <code>0</code>. For 567backward compatibility reasons,<code>'IPv4'</code> and <code>'IPv6'</code> are interpreted as <code>4</code> 568and <code>6</code> respectively. The value <code>0</code> indicates that IPv4 and IPv6 addresses 569are both returned. <strong>Default:</strong> <code>0</code>.</li> 570<li><code>hints</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> One or more <a href="#supported-getaddrinfo-flags">supported <code>getaddrinfo</code> flags</a>. Multiple 571flags may be passed by bitwise <code>OR</code>ing their values.</li> 572<li><code>all</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, the callback returns all resolved addresses in 573an array. Otherwise, returns a single address. <strong>Default:</strong> <code>false</code>.</li> 574<li><code>verbatim</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, the callback receives IPv4 and IPv6 575addresses in the order the DNS resolver returned them. When <code>false</code>, 576IPv4 addresses are placed before IPv6 addresses. 577<strong>Default:</strong> <code>true</code> (addresses are not reordered). Default value is 578configurable using <a href="#dnssetdefaultresultorderorder"><code>dns.setDefaultResultOrder()</code></a> or 579<a href="cli.html#--dns-result-orderorder"><code>--dns-result-order</code></a>.</li> 580</ul> 581</li> 582<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 583<ul> 584<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 585<li><code>address</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> A string representation of an IPv4 or IPv6 address.</li> 586<li><code>family</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <code>4</code> or <code>6</code>, denoting the family of <code>address</code>, or <code>0</code> if 587the address is not an IPv4 or IPv6 address. <code>0</code> is a likely indicator of a 588bug in the name resolution service used by the operating system.</li> 589</ul> 590</li> 591</ul> 592<p>Resolves a host name (e.g. <code>'nodejs.org'</code>) into the first found A (IPv4) or 593AAAA (IPv6) record. All <code>option</code> properties are optional. If <code>options</code> is an 594integer, then it must be <code>4</code> or <code>6</code> – if <code>options</code> is <code>0</code> or not provided, then 595IPv4 and IPv6 addresses are both returned if found.</p> 596<p>With the <code>all</code> option set to <code>true</code>, the arguments for <code>callback</code> change to 597<code>(err, addresses)</code>, with <code>addresses</code> being an array of objects with the 598properties <code>address</code> and <code>family</code>.</p> 599<p>On error, <code>err</code> is an <a href="errors.html#class-error"><code>Error</code></a> object, where <code>err.code</code> is the error code. 600Keep in mind that <code>err.code</code> will be set to <code>'ENOTFOUND'</code> not only when 601the host name does not exist but also when the lookup fails in other ways 602such as no available file descriptors.</p> 603<p><code>dns.lookup()</code> does not necessarily have anything to do with the DNS protocol. 604The implementation uses an operating system facility that can associate names 605with addresses and vice versa. This implementation can have subtle but 606important consequences on the behavior of any Node.js program. Please take some 607time to consult the <a href="#implementation-considerations">Implementation considerations section</a> before using 608<code>dns.lookup()</code>.</p> 609<p>Example usage:</p> 610<pre><code class="language-js"><span class="hljs-keyword">const</span> dns = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:dns'</span>); 611<span class="hljs-keyword">const</span> options = { 612 <span class="hljs-attr">family</span>: <span class="hljs-number">6</span>, 613 <span class="hljs-attr">hints</span>: dns.<span class="hljs-property">ADDRCONFIG</span> | dns.<span class="hljs-property">V4MAPPED</span>, 614}; 615dns.<span class="hljs-title function_">lookup</span>(<span class="hljs-string">'example.com'</span>, options, <span class="hljs-function">(<span class="hljs-params">err, address, family</span>) =></span> 616 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'address: %j family: IPv%s'</span>, address, family)); 617<span class="hljs-comment">// address: "2606:2800:220:1:248:1893:25c8:1946" family: IPv6</span> 618 619<span class="hljs-comment">// When options.all is true, the result will be an Array.</span> 620options.<span class="hljs-property">all</span> = <span class="hljs-literal">true</span>; 621dns.<span class="hljs-title function_">lookup</span>(<span class="hljs-string">'example.com'</span>, options, <span class="hljs-function">(<span class="hljs-params">err, addresses</span>) =></span> 622 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'addresses: %j'</span>, addresses)); 623<span class="hljs-comment">// addresses: [{"address":"2606:2800:220:1:248:1893:25c8:1946","family":6}]</span></code> <button class="copy-button">copy</button></pre> 624<p>If this method is invoked as its <a href="util.html#utilpromisifyoriginal"><code>util.promisify()</code></a>ed version, and <code>all</code> 625is not set to <code>true</code>, it returns a <code>Promise</code> for an <code>Object</code> with <code>address</code> and 626<code>family</code> properties.</p> 627<h4>Supported getaddrinfo flags<span><a class="mark" href="#supported-getaddrinfo-flags" id="supported-getaddrinfo-flags">#</a></span><a aria-hidden="true" class="legacy" id="dns_supported_getaddrinfo_flags"></a></h4> 628<div class="api_metadata"> 629<details class="changelog"><summary>History</summary> 630<table> 631<tbody><tr><th>Version</th><th>Changes</th></tr> 632<tr><td>v13.13.0, v12.17.0</td> 633<td><p>Added support for the <code>dns.ALL</code> flag.</p></td></tr> 634</tbody></table> 635</details> 636</div> 637<p>The following flags can be passed as hints to <a href="#dnslookuphostname-options-callback"><code>dns.lookup()</code></a>.</p> 638<ul> 639<li><code>dns.ADDRCONFIG</code>: Limits returned address types to the types of non-loopback 640addresses configured on the system. For example, IPv4 addresses are only 641returned if the current system has at least one IPv4 address configured.</li> 642<li><code>dns.V4MAPPED</code>: If the IPv6 family was specified, but no IPv6 addresses were 643found, then return IPv4 mapped IPv6 addresses. It is not supported 644on some operating systems (e.g. FreeBSD 10.1).</li> 645<li><code>dns.ALL</code>: If <code>dns.V4MAPPED</code> is specified, return resolved IPv6 addresses as 646well as IPv4 mapped IPv6 addresses.</li> 647</ul> 648</section><section><h3><code>dns.lookupService(address, port, callback)</code><span><a class="mark" href="#dnslookupserviceaddress-port-callback" id="dnslookupserviceaddress-port-callback">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_lookupservice_address_port_callback"></a></h3> 649<div class="api_metadata"> 650<details class="changelog"><summary>History</summary> 651<table> 652<tbody><tr><th>Version</th><th>Changes</th></tr> 653<tr><td>v18.0.0</td> 654<td><p>Passing an invalid callback to the <code>callback</code> argument now throws <code>ERR_INVALID_ARG_TYPE</code> instead of <code>ERR_INVALID_CALLBACK</code>.</p></td></tr> 655<tr><td>v0.11.14</td> 656<td><p><span>Added in: v0.11.14</span></p></td></tr> 657</tbody></table> 658</details> 659</div> 660<ul> 661<li><code>address</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 662<li><code>port</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 663<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 664<ul> 665<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 666<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> e.g. <code>example.com</code></li> 667<li><code>service</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> e.g. <code>http</code></li> 668</ul> 669</li> 670</ul> 671<p>Resolves the given <code>address</code> and <code>port</code> into a host name and service using 672the operating system's underlying <code>getnameinfo</code> implementation.</p> 673<p>If <code>address</code> is not a valid IP address, a <code>TypeError</code> will be thrown. 674The <code>port</code> will be coerced to a number. If it is not a legal port, a <code>TypeError</code> 675will be thrown.</p> 676<p>On an error, <code>err</code> is an <a href="errors.html#class-error"><code>Error</code></a> object, where <code>err.code</code> is the error code.</p> 677<pre><code class="language-js"><span class="hljs-keyword">const</span> dns = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:dns'</span>); 678dns.<span class="hljs-title function_">lookupService</span>(<span class="hljs-string">'127.0.0.1'</span>, <span class="hljs-number">22</span>, <span class="hljs-function">(<span class="hljs-params">err, hostname, service</span>) =></span> { 679 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(hostname, service); 680 <span class="hljs-comment">// Prints: localhost ssh</span> 681});</code> <button class="copy-button">copy</button></pre> 682<p>If this method is invoked as its <a href="util.html#utilpromisifyoriginal"><code>util.promisify()</code></a>ed version, it returns a 683<code>Promise</code> for an <code>Object</code> with <code>hostname</code> and <code>service</code> properties.</p> 684</section><section><h3><code>dns.resolve(hostname[, rrtype], callback)</code><span><a class="mark" href="#dnsresolvehostname-rrtype-callback" id="dnsresolvehostname-rrtype-callback">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_resolve_hostname_rrtype_callback"></a></h3> 685<div class="api_metadata"> 686<details class="changelog"><summary>History</summary> 687<table> 688<tbody><tr><th>Version</th><th>Changes</th></tr> 689<tr><td>v18.0.0</td> 690<td><p>Passing an invalid callback to the <code>callback</code> argument now throws <code>ERR_INVALID_ARG_TYPE</code> instead of <code>ERR_INVALID_CALLBACK</code>.</p></td></tr> 691<tr><td>v0.1.27</td> 692<td><p><span>Added in: v0.1.27</span></p></td></tr> 693</tbody></table> 694</details> 695</div> 696<ul> 697<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Host name to resolve.</li> 698<li><code>rrtype</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Resource record type. <strong>Default:</strong> <code>'A'</code>.</li> 699<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 700<ul> 701<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 702<li><code>records</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object[]></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 703</ul> 704</li> 705</ul> 706<p>Uses the DNS protocol to resolve a host name (e.g. <code>'nodejs.org'</code>) into an array 707of the resource records. The <code>callback</code> function has arguments 708<code>(err, records)</code>. When successful, <code>records</code> will be an array of resource 709records. The type and structure of individual results varies based on <code>rrtype</code>:</p> 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793<table><thead><tr><th><code>rrtype</code></th><th><code>records</code> contains</th><th>Result type</th><th>Shorthand method</th></tr></thead><tbody><tr><td><code>'A'</code></td><td>IPv4 addresses (default)</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></td><td><a href="#dnsresolve4hostname-options-callback"><code>dns.resolve4()</code></a></td></tr><tr><td><code>'AAAA'</code></td><td>IPv6 addresses</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></td><td><a href="#dnsresolve6hostname-options-callback"><code>dns.resolve6()</code></a></td></tr><tr><td><code>'ANY'</code></td><td>any records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dnsresolveanyhostname-callback"><code>dns.resolveAny()</code></a></td></tr><tr><td><code>'CAA'</code></td><td>CA authorization records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dnsresolvecaahostname-callback"><code>dns.resolveCaa()</code></a></td></tr><tr><td><code>'CNAME'</code></td><td>canonical name records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></td><td><a href="#dnsresolvecnamehostname-callback"><code>dns.resolveCname()</code></a></td></tr><tr><td><code>'MX'</code></td><td>mail exchange records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dnsresolvemxhostname-callback"><code>dns.resolveMx()</code></a></td></tr><tr><td><code>'NAPTR'</code></td><td>name authority pointer records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dnsresolvenaptrhostname-callback"><code>dns.resolveNaptr()</code></a></td></tr><tr><td><code>'NS'</code></td><td>name server records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></td><td><a href="#dnsresolvenshostname-callback"><code>dns.resolveNs()</code></a></td></tr><tr><td><code>'PTR'</code></td><td>pointer records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></td><td><a href="#dnsresolveptrhostname-callback"><code>dns.resolvePtr()</code></a></td></tr><tr><td><code>'SOA'</code></td><td>start of authority records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dnsresolvesoahostname-callback"><code>dns.resolveSoa()</code></a></td></tr><tr><td><code>'SRV'</code></td><td>service records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dnsresolvesrvhostname-callback"><code>dns.resolveSrv()</code></a></td></tr><tr><td><code>'TXT'</code></td><td>text records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></td><td><a href="#dnsresolvetxthostname-callback"><code>dns.resolveTxt()</code></a></td></tr></tbody></table> 794<p>On error, <code>err</code> is an <a href="errors.html#class-error"><code>Error</code></a> object, where <code>err.code</code> is one of the 795<a href="#error-codes">DNS error codes</a>.</p> 796</section><section><h3><code>dns.resolve4(hostname[, options], callback)</code><span><a class="mark" href="#dnsresolve4hostname-options-callback" id="dnsresolve4hostname-options-callback">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_resolve4_hostname_options_callback"></a></h3> 797<div class="api_metadata"> 798<details class="changelog"><summary>History</summary> 799<table> 800<tbody><tr><th>Version</th><th>Changes</th></tr> 801<tr><td>v18.0.0</td> 802<td><p>Passing an invalid callback to the <code>callback</code> argument now throws <code>ERR_INVALID_ARG_TYPE</code> instead of <code>ERR_INVALID_CALLBACK</code>.</p></td></tr> 803<tr><td>v7.2.0</td> 804<td><p>This method now supports passing <code>options</code>, specifically <code>options.ttl</code>.</p></td></tr> 805<tr><td>v0.1.16</td> 806<td><p><span>Added in: v0.1.16</span></p></td></tr> 807</tbody></table> 808</details> 809</div> 810<ul> 811<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Host name to resolve.</li> 812<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 813<ul> 814<li><code>ttl</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Retrieves the Time-To-Live value (TTL) of each record. 815When <code>true</code>, the callback receives an array of 816<code>{ address: '1.2.3.4', ttl: 60 }</code> objects rather than an array of strings, 817with the TTL expressed in seconds.</li> 818</ul> 819</li> 820<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 821<ul> 822<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 823<li><code>addresses</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object[]></a></li> 824</ul> 825</li> 826</ul> 827<p>Uses the DNS protocol to resolve a IPv4 addresses (<code>A</code> records) for the 828<code>hostname</code>. The <code>addresses</code> argument passed to the <code>callback</code> function 829will contain an array of IPv4 addresses (e.g. 830<code>['74.125.79.104', '74.125.79.105', '74.125.79.106']</code>).</p> 831</section><section><h3><code>dns.resolve6(hostname[, options], callback)</code><span><a class="mark" href="#dnsresolve6hostname-options-callback" id="dnsresolve6hostname-options-callback">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_resolve6_hostname_options_callback"></a></h3> 832<div class="api_metadata"> 833<details class="changelog"><summary>History</summary> 834<table> 835<tbody><tr><th>Version</th><th>Changes</th></tr> 836<tr><td>v18.0.0</td> 837<td><p>Passing an invalid callback to the <code>callback</code> argument now throws <code>ERR_INVALID_ARG_TYPE</code> instead of <code>ERR_INVALID_CALLBACK</code>.</p></td></tr> 838<tr><td>v7.2.0</td> 839<td><p>This method now supports passing <code>options</code>, specifically <code>options.ttl</code>.</p></td></tr> 840<tr><td>v0.1.16</td> 841<td><p><span>Added in: v0.1.16</span></p></td></tr> 842</tbody></table> 843</details> 844</div> 845<ul> 846<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Host name to resolve.</li> 847<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 848<ul> 849<li><code>ttl</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Retrieve the Time-To-Live value (TTL) of each record. 850When <code>true</code>, the callback receives an array of 851<code>{ address: '0:1:2:3:4:5:6:7', ttl: 60 }</code> objects rather than an array of 852strings, with the TTL expressed in seconds.</li> 853</ul> 854</li> 855<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 856<ul> 857<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 858<li><code>addresses</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object[]></a></li> 859</ul> 860</li> 861</ul> 862<p>Uses the DNS protocol to resolve IPv6 addresses (<code>AAAA</code> records) for the 863<code>hostname</code>. The <code>addresses</code> argument passed to the <code>callback</code> function 864will contain an array of IPv6 addresses.</p> 865</section><section><h3><code>dns.resolveAny(hostname, callback)</code><span><a class="mark" href="#dnsresolveanyhostname-callback" id="dnsresolveanyhostname-callback">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_resolveany_hostname_callback"></a></h3> 866<div class="api_metadata"> 867<details class="changelog"><summary>History</summary> 868<table> 869<tbody><tr><th>Version</th><th>Changes</th></tr> 870<tr><td>v18.0.0</td> 871<td><p>Passing an invalid callback to the <code>callback</code> argument now throws <code>ERR_INVALID_ARG_TYPE</code> instead of <code>ERR_INVALID_CALLBACK</code>.</p></td></tr> 872</tbody></table> 873</details> 874</div> 875<ul> 876<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 877<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 878<ul> 879<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 880<li><code>ret</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object[]></a></li> 881</ul> 882</li> 883</ul> 884<p>Uses the DNS protocol to resolve all records (also known as <code>ANY</code> or <code>*</code> query). 885The <code>ret</code> argument passed to the <code>callback</code> function will be an array containing 886various types of records. Each object has a property <code>type</code> that indicates the 887type of the current record. And depending on the <code>type</code>, additional properties 888will be present on the object:</p> 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938<table><thead><tr><th>Type</th><th>Properties</th></tr></thead><tbody><tr><td><code>'A'</code></td><td><code>address</code>/<code>ttl</code></td></tr><tr><td><code>'AAAA'</code></td><td><code>address</code>/<code>ttl</code></td></tr><tr><td><code>'CNAME'</code></td><td><code>value</code></td></tr><tr><td><code>'MX'</code></td><td>Refer to <a href="#dnsresolvemxhostname-callback"><code>dns.resolveMx()</code></a></td></tr><tr><td><code>'NAPTR'</code></td><td>Refer to <a href="#dnsresolvenaptrhostname-callback"><code>dns.resolveNaptr()</code></a></td></tr><tr><td><code>'NS'</code></td><td><code>value</code></td></tr><tr><td><code>'PTR'</code></td><td><code>value</code></td></tr><tr><td><code>'SOA'</code></td><td>Refer to <a href="#dnsresolvesoahostname-callback"><code>dns.resolveSoa()</code></a></td></tr><tr><td><code>'SRV'</code></td><td>Refer to <a href="#dnsresolvesrvhostname-callback"><code>dns.resolveSrv()</code></a></td></tr><tr><td><code>'TXT'</code></td><td>This type of record contains an array property called <code>entries</code> which refers to <a href="#dnsresolvetxthostname-callback"><code>dns.resolveTxt()</code></a>, e.g. <code>{ entries: ['...'], type: 'TXT' }</code></td></tr></tbody></table> 939<p>Here is an example of the <code>ret</code> object passed to the callback:</p> 940<!-- eslint-disable semi --> 941<pre><code class="language-js">[ { <span class="hljs-attr">type</span>: <span class="hljs-string">'A'</span>, <span class="hljs-attr">address</span>: <span class="hljs-string">'127.0.0.1'</span>, <span class="hljs-attr">ttl</span>: <span class="hljs-number">299</span> }, 942 { <span class="hljs-attr">type</span>: <span class="hljs-string">'CNAME'</span>, <span class="hljs-attr">value</span>: <span class="hljs-string">'example.com'</span> }, 943 { <span class="hljs-attr">type</span>: <span class="hljs-string">'MX'</span>, <span class="hljs-attr">exchange</span>: <span class="hljs-string">'alt4.aspmx.l.example.com'</span>, <span class="hljs-attr">priority</span>: <span class="hljs-number">50</span> }, 944 { <span class="hljs-attr">type</span>: <span class="hljs-string">'NS'</span>, <span class="hljs-attr">value</span>: <span class="hljs-string">'ns1.example.com'</span> }, 945 { <span class="hljs-attr">type</span>: <span class="hljs-string">'TXT'</span>, <span class="hljs-attr">entries</span>: [ <span class="hljs-string">'v=spf1 include:_spf.example.com ~all'</span> ] }, 946 { <span class="hljs-attr">type</span>: <span class="hljs-string">'SOA'</span>, 947 <span class="hljs-attr">nsname</span>: <span class="hljs-string">'ns1.example.com'</span>, 948 <span class="hljs-attr">hostmaster</span>: <span class="hljs-string">'admin.example.com'</span>, 949 <span class="hljs-attr">serial</span>: <span class="hljs-number">156696742</span>, 950 <span class="hljs-attr">refresh</span>: <span class="hljs-number">900</span>, 951 <span class="hljs-attr">retry</span>: <span class="hljs-number">900</span>, 952 <span class="hljs-attr">expire</span>: <span class="hljs-number">1800</span>, 953 <span class="hljs-attr">minttl</span>: <span class="hljs-number">60</span> } ]</code> <button class="copy-button">copy</button></pre> 954<p>DNS server operators may choose not to respond to <code>ANY</code> 955queries. It may be better to call individual methods like <a href="#dnsresolve4hostname-options-callback"><code>dns.resolve4()</code></a>, 956<a href="#dnsresolvemxhostname-callback"><code>dns.resolveMx()</code></a>, and so on. For more details, see <a href="https://tools.ietf.org/html/rfc8482">RFC 8482</a>.</p> 957</section><section><h3><code>dns.resolveCname(hostname, callback)</code><span><a class="mark" href="#dnsresolvecnamehostname-callback" id="dnsresolvecnamehostname-callback">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_resolvecname_hostname_callback"></a></h3> 958<div class="api_metadata"> 959<details class="changelog"><summary>History</summary> 960<table> 961<tbody><tr><th>Version</th><th>Changes</th></tr> 962<tr><td>v18.0.0</td> 963<td><p>Passing an invalid callback to the <code>callback</code> argument now throws <code>ERR_INVALID_ARG_TYPE</code> instead of <code>ERR_INVALID_CALLBACK</code>.</p></td></tr> 964<tr><td>v0.3.2</td> 965<td><p><span>Added in: v0.3.2</span></p></td></tr> 966</tbody></table> 967</details> 968</div> 969<ul> 970<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 971<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 972<ul> 973<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 974<li><code>addresses</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li> 975</ul> 976</li> 977</ul> 978<p>Uses the DNS protocol to resolve <code>CNAME</code> records for the <code>hostname</code>. The 979<code>addresses</code> argument passed to the <code>callback</code> function 980will contain an array of canonical name records available for the <code>hostname</code> 981(e.g. <code>['bar.example.com']</code>).</p> 982</section><section><h3><code>dns.resolveCaa(hostname, callback)</code><span><a class="mark" href="#dnsresolvecaahostname-callback" id="dnsresolvecaahostname-callback">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_resolvecaa_hostname_callback"></a></h3> 983<div class="api_metadata"> 984<details class="changelog"><summary>History</summary> 985<table> 986<tbody><tr><th>Version</th><th>Changes</th></tr> 987<tr><td>v18.0.0</td> 988<td><p>Passing an invalid callback to the <code>callback</code> argument now throws <code>ERR_INVALID_ARG_TYPE</code> instead of <code>ERR_INVALID_CALLBACK</code>.</p></td></tr> 989<tr><td>v15.0.0, v14.17.0</td> 990<td><p><span>Added in: v15.0.0, v14.17.0</span></p></td></tr> 991</tbody></table> 992</details> 993</div> 994<ul> 995<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 996<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 997<ul> 998<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 999<li><code>records</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object[]></a></li> 1000</ul> 1001</li> 1002</ul> 1003<p>Uses the DNS protocol to resolve <code>CAA</code> records for the <code>hostname</code>. The 1004<code>addresses</code> argument passed to the <code>callback</code> function 1005will contain an array of certification authority authorization records 1006available for the <code>hostname</code> (e.g. <code>[{critical: 0, iodef: 'mailto:pki@example.com'}, {critical: 128, issue: 'pki.example.com'}]</code>).</p> 1007</section><section><h3><code>dns.resolveMx(hostname, callback)</code><span><a class="mark" href="#dnsresolvemxhostname-callback" id="dnsresolvemxhostname-callback">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_resolvemx_hostname_callback"></a></h3> 1008<div class="api_metadata"> 1009<details class="changelog"><summary>History</summary> 1010<table> 1011<tbody><tr><th>Version</th><th>Changes</th></tr> 1012<tr><td>v18.0.0</td> 1013<td><p>Passing an invalid callback to the <code>callback</code> argument now throws <code>ERR_INVALID_ARG_TYPE</code> instead of <code>ERR_INVALID_CALLBACK</code>.</p></td></tr> 1014<tr><td>v0.1.27</td> 1015<td><p><span>Added in: v0.1.27</span></p></td></tr> 1016</tbody></table> 1017</details> 1018</div> 1019<ul> 1020<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1021<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 1022<ul> 1023<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 1024<li><code>addresses</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object[]></a></li> 1025</ul> 1026</li> 1027</ul> 1028<p>Uses the DNS protocol to resolve mail exchange records (<code>MX</code> records) for the 1029<code>hostname</code>. The <code>addresses</code> argument passed to the <code>callback</code> function will 1030contain an array of objects containing both a <code>priority</code> and <code>exchange</code> 1031property (e.g. <code>[{priority: 10, exchange: 'mx.example.com'}, ...]</code>).</p> 1032</section><section><h3><code>dns.resolveNaptr(hostname, callback)</code><span><a class="mark" href="#dnsresolvenaptrhostname-callback" id="dnsresolvenaptrhostname-callback">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_resolvenaptr_hostname_callback"></a></h3> 1033<div class="api_metadata"> 1034<details class="changelog"><summary>History</summary> 1035<table> 1036<tbody><tr><th>Version</th><th>Changes</th></tr> 1037<tr><td>v18.0.0</td> 1038<td><p>Passing an invalid callback to the <code>callback</code> argument now throws <code>ERR_INVALID_ARG_TYPE</code> instead of <code>ERR_INVALID_CALLBACK</code>.</p></td></tr> 1039<tr><td>v0.9.12</td> 1040<td><p><span>Added in: v0.9.12</span></p></td></tr> 1041</tbody></table> 1042</details> 1043</div> 1044<ul> 1045<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1046<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 1047<ul> 1048<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 1049<li><code>addresses</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object[]></a></li> 1050</ul> 1051</li> 1052</ul> 1053<p>Uses the DNS protocol to resolve regular expression-based records (<code>NAPTR</code> 1054records) for the <code>hostname</code>. The <code>addresses</code> argument passed to the <code>callback</code> 1055function will contain an array of objects with the following properties:</p> 1056<ul> 1057<li><code>flags</code></li> 1058<li><code>service</code></li> 1059<li><code>regexp</code></li> 1060<li><code>replacement</code></li> 1061<li><code>order</code></li> 1062<li><code>preference</code></li> 1063</ul> 1064<!-- eslint-skip --> 1065<pre><code class="language-js">{ 1066 <span class="hljs-attr">flags</span>: <span class="hljs-string">'s'</span>, 1067 <span class="hljs-attr">service</span>: <span class="hljs-string">'SIP+D2U'</span>, 1068 <span class="hljs-attr">regexp</span>: <span class="hljs-string">''</span>, 1069 <span class="hljs-attr">replacement</span>: <span class="hljs-string">'_sip._udp.example.com'</span>, 1070 <span class="hljs-attr">order</span>: <span class="hljs-number">30</span>, 1071 <span class="hljs-attr">preference</span>: <span class="hljs-number">100</span> 1072}</code> <button class="copy-button">copy</button></pre> 1073</section><section><h3><code>dns.resolveNs(hostname, callback)</code><span><a class="mark" href="#dnsresolvenshostname-callback" id="dnsresolvenshostname-callback">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_resolvens_hostname_callback"></a></h3> 1074<div class="api_metadata"> 1075<details class="changelog"><summary>History</summary> 1076<table> 1077<tbody><tr><th>Version</th><th>Changes</th></tr> 1078<tr><td>v18.0.0</td> 1079<td><p>Passing an invalid callback to the <code>callback</code> argument now throws <code>ERR_INVALID_ARG_TYPE</code> instead of <code>ERR_INVALID_CALLBACK</code>.</p></td></tr> 1080<tr><td>v0.1.90</td> 1081<td><p><span>Added in: v0.1.90</span></p></td></tr> 1082</tbody></table> 1083</details> 1084</div> 1085<ul> 1086<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1087<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 1088<ul> 1089<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 1090<li><code>addresses</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li> 1091</ul> 1092</li> 1093</ul> 1094<p>Uses the DNS protocol to resolve name server records (<code>NS</code> records) for the 1095<code>hostname</code>. The <code>addresses</code> argument passed to the <code>callback</code> function will 1096contain an array of name server records available for <code>hostname</code> 1097(e.g. <code>['ns1.example.com', 'ns2.example.com']</code>).</p> 1098</section><section><h3><code>dns.resolvePtr(hostname, callback)</code><span><a class="mark" href="#dnsresolveptrhostname-callback" id="dnsresolveptrhostname-callback">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_resolveptr_hostname_callback"></a></h3> 1099<div class="api_metadata"> 1100<details class="changelog"><summary>History</summary> 1101<table> 1102<tbody><tr><th>Version</th><th>Changes</th></tr> 1103<tr><td>v18.0.0</td> 1104<td><p>Passing an invalid callback to the <code>callback</code> argument now throws <code>ERR_INVALID_ARG_TYPE</code> instead of <code>ERR_INVALID_CALLBACK</code>.</p></td></tr> 1105<tr><td>v6.0.0</td> 1106<td><p><span>Added in: v6.0.0</span></p></td></tr> 1107</tbody></table> 1108</details> 1109</div> 1110<ul> 1111<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1112<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 1113<ul> 1114<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 1115<li><code>addresses</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li> 1116</ul> 1117</li> 1118</ul> 1119<p>Uses the DNS protocol to resolve pointer records (<code>PTR</code> records) for the 1120<code>hostname</code>. The <code>addresses</code> argument passed to the <code>callback</code> function will 1121be an array of strings containing the reply records.</p> 1122</section><section><h3><code>dns.resolveSoa(hostname, callback)</code><span><a class="mark" href="#dnsresolvesoahostname-callback" id="dnsresolvesoahostname-callback">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_resolvesoa_hostname_callback"></a></h3> 1123<div class="api_metadata"> 1124<details class="changelog"><summary>History</summary> 1125<table> 1126<tbody><tr><th>Version</th><th>Changes</th></tr> 1127<tr><td>v18.0.0</td> 1128<td><p>Passing an invalid callback to the <code>callback</code> argument now throws <code>ERR_INVALID_ARG_TYPE</code> instead of <code>ERR_INVALID_CALLBACK</code>.</p></td></tr> 1129<tr><td>v0.11.10</td> 1130<td><p><span>Added in: v0.11.10</span></p></td></tr> 1131</tbody></table> 1132</details> 1133</div> 1134<ul> 1135<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1136<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 1137<ul> 1138<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 1139<li><code>address</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 1140</ul> 1141</li> 1142</ul> 1143<p>Uses the DNS protocol to resolve a start of authority record (<code>SOA</code> record) for 1144the <code>hostname</code>. The <code>address</code> argument passed to the <code>callback</code> function will 1145be an object with the following properties:</p> 1146<ul> 1147<li><code>nsname</code></li> 1148<li><code>hostmaster</code></li> 1149<li><code>serial</code></li> 1150<li><code>refresh</code></li> 1151<li><code>retry</code></li> 1152<li><code>expire</code></li> 1153<li><code>minttl</code></li> 1154</ul> 1155<!-- eslint-skip --> 1156<pre><code class="language-js">{ 1157 <span class="hljs-attr">nsname</span>: <span class="hljs-string">'ns.example.com'</span>, 1158 <span class="hljs-attr">hostmaster</span>: <span class="hljs-string">'root.example.com'</span>, 1159 <span class="hljs-attr">serial</span>: <span class="hljs-number">2013101809</span>, 1160 <span class="hljs-attr">refresh</span>: <span class="hljs-number">10000</span>, 1161 <span class="hljs-attr">retry</span>: <span class="hljs-number">2400</span>, 1162 <span class="hljs-attr">expire</span>: <span class="hljs-number">604800</span>, 1163 <span class="hljs-attr">minttl</span>: <span class="hljs-number">3600</span> 1164}</code> <button class="copy-button">copy</button></pre> 1165</section><section><h3><code>dns.resolveSrv(hostname, callback)</code><span><a class="mark" href="#dnsresolvesrvhostname-callback" id="dnsresolvesrvhostname-callback">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_resolvesrv_hostname_callback"></a></h3> 1166<div class="api_metadata"> 1167<details class="changelog"><summary>History</summary> 1168<table> 1169<tbody><tr><th>Version</th><th>Changes</th></tr> 1170<tr><td>v18.0.0</td> 1171<td><p>Passing an invalid callback to the <code>callback</code> argument now throws <code>ERR_INVALID_ARG_TYPE</code> instead of <code>ERR_INVALID_CALLBACK</code>.</p></td></tr> 1172<tr><td>v0.1.27</td> 1173<td><p><span>Added in: v0.1.27</span></p></td></tr> 1174</tbody></table> 1175</details> 1176</div> 1177<ul> 1178<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1179<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 1180<ul> 1181<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 1182<li><code>addresses</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object[]></a></li> 1183</ul> 1184</li> 1185</ul> 1186<p>Uses the DNS protocol to resolve service records (<code>SRV</code> records) for the 1187<code>hostname</code>. The <code>addresses</code> argument passed to the <code>callback</code> function will 1188be an array of objects with the following properties:</p> 1189<ul> 1190<li><code>priority</code></li> 1191<li><code>weight</code></li> 1192<li><code>port</code></li> 1193<li><code>name</code></li> 1194</ul> 1195<!-- eslint-skip --> 1196<pre><code class="language-js">{ 1197 <span class="hljs-attr">priority</span>: <span class="hljs-number">10</span>, 1198 <span class="hljs-attr">weight</span>: <span class="hljs-number">5</span>, 1199 <span class="hljs-attr">port</span>: <span class="hljs-number">21223</span>, 1200 <span class="hljs-attr">name</span>: <span class="hljs-string">'service.example.com'</span> 1201}</code> <button class="copy-button">copy</button></pre> 1202</section><section><h3><code>dns.resolveTxt(hostname, callback)</code><span><a class="mark" href="#dnsresolvetxthostname-callback" id="dnsresolvetxthostname-callback">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_resolvetxt_hostname_callback"></a></h3> 1203<div class="api_metadata"> 1204<details class="changelog"><summary>History</summary> 1205<table> 1206<tbody><tr><th>Version</th><th>Changes</th></tr> 1207<tr><td>v18.0.0</td> 1208<td><p>Passing an invalid callback to the <code>callback</code> argument now throws <code>ERR_INVALID_ARG_TYPE</code> instead of <code>ERR_INVALID_CALLBACK</code>.</p></td></tr> 1209<tr><td>v0.1.27</td> 1210<td><p><span>Added in: v0.1.27</span></p></td></tr> 1211</tbody></table> 1212</details> 1213</div> 1214<!--lint disable no-undefined-references list-item-bullet-indent--> 1215<ul> 1216<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1217<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 1218<ul> 1219<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 1220<li><code>records</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[][]></a></li> 1221</ul> 1222</li> 1223</ul> 1224<!--lint enable no-undefined-references list-item-bullet-indent--> 1225<p>Uses the DNS protocol to resolve text queries (<code>TXT</code> records) for the 1226<code>hostname</code>. The <code>records</code> argument passed to the <code>callback</code> function is a 1227two-dimensional array of the text records available for <code>hostname</code> (e.g. 1228<code>[ ['v=spf1 ip4:0.0.0.0 ', '~all' ] ]</code>). Each sub-array contains TXT chunks of 1229one record. Depending on the use case, these could be either joined together or 1230treated separately.</p> 1231</section><section><h3><code>dns.reverse(ip, callback)</code><span><a class="mark" href="#dnsreverseip-callback" id="dnsreverseip-callback">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_reverse_ip_callback"></a></h3> 1232<div class="api_metadata"> 1233<span>Added in: v0.1.16</span> 1234</div> 1235<ul> 1236<li><code>ip</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1237<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 1238<ul> 1239<li><code>err</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 1240<li><code>hostnames</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li> 1241</ul> 1242</li> 1243</ul> 1244<p>Performs a reverse DNS query that resolves an IPv4 or IPv6 address to an 1245array of host names.</p> 1246<p>On error, <code>err</code> is an <a href="errors.html#class-error"><code>Error</code></a> object, where <code>err.code</code> is 1247one of the <a href="#error-codes">DNS error codes</a>.</p> 1248</section><section><h3><code>dns.setDefaultResultOrder(order)</code><span><a class="mark" href="#dnssetdefaultresultorderorder" id="dnssetdefaultresultorderorder">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_setdefaultresultorder_order"></a></h3> 1249<div class="api_metadata"> 1250<details class="changelog"><summary>History</summary> 1251<table> 1252<tbody><tr><th>Version</th><th>Changes</th></tr> 1253<tr><td>v17.0.0</td> 1254<td><p>Changed default value to <code>verbatim</code>.</p></td></tr> 1255<tr><td>v16.4.0, v14.18.0</td> 1256<td><p><span>Added in: v16.4.0, v14.18.0</span></p></td></tr> 1257</tbody></table> 1258</details> 1259</div> 1260<ul> 1261<li><code>order</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> must be <code>'ipv4first'</code> or <code>'verbatim'</code>.</li> 1262</ul> 1263<p>Set the default value of <code>verbatim</code> in <a href="#dnslookuphostname-options-callback"><code>dns.lookup()</code></a> and 1264<a href="#dnspromiseslookuphostname-options"><code>dnsPromises.lookup()</code></a>. The value could be:</p> 1265<ul> 1266<li><code>ipv4first</code>: sets default <code>verbatim</code> <code>false</code>.</li> 1267<li><code>verbatim</code>: sets default <code>verbatim</code> <code>true</code>.</li> 1268</ul> 1269<p>The default is <code>verbatim</code> and <a href="#dnssetdefaultresultorderorder"><code>dns.setDefaultResultOrder()</code></a> have higher 1270priority than <a href="cli.html#--dns-result-orderorder"><code>--dns-result-order</code></a>. When using <a href="worker_threads.html">worker threads</a>, 1271<a href="#dnssetdefaultresultorderorder"><code>dns.setDefaultResultOrder()</code></a> from the main thread won't affect the default 1272dns orders in workers.</p> 1273</section><section><h3><code>dns.getDefaultResultOrder()</code><span><a class="mark" href="#dnsgetdefaultresultorder" id="dnsgetdefaultresultorder">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_getdefaultresultorder"></a></h3> 1274<div class="api_metadata"> 1275<span>Added in: v18.17.0</span> 1276</div> 1277<p>Get the default value for <code>verbatim</code> in <a href="#dnslookuphostname-options-callback"><code>dns.lookup()</code></a> and 1278<a href="#dnspromiseslookuphostname-options"><code>dnsPromises.lookup()</code></a>. The value could be:</p> 1279<ul> 1280<li><code>ipv4first</code>: for <code>verbatim</code> defaulting to <code>false</code>.</li> 1281<li><code>verbatim</code>: for <code>verbatim</code> defaulting to <code>true</code>.</li> 1282</ul> 1283</section><section><h3><code>dns.setServers(servers)</code><span><a class="mark" href="#dnssetserversservers" id="dnssetserversservers">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_setservers_servers"></a></h3> 1284<div class="api_metadata"> 1285<span>Added in: v0.11.3</span> 1286</div> 1287<ul> 1288<li><code>servers</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a> array of <a href="https://tools.ietf.org/html/rfc5952#section-6">RFC 5952</a> formatted addresses</li> 1289</ul> 1290<p>Sets the IP address and port of servers to be used when performing DNS 1291resolution. The <code>servers</code> argument is an array of <a href="https://tools.ietf.org/html/rfc5952#section-6">RFC 5952</a> formatted 1292addresses. If the port is the IANA default DNS port (53) it can be omitted.</p> 1293<pre><code class="language-js">dns.<span class="hljs-title function_">setServers</span>([ 1294 <span class="hljs-string">'4.4.4.4'</span>, 1295 <span class="hljs-string">'[2001:4860:4860::8888]'</span>, 1296 <span class="hljs-string">'4.4.4.4:1053'</span>, 1297 <span class="hljs-string">'[2001:4860:4860::8888]:1053'</span>, 1298]);</code> <button class="copy-button">copy</button></pre> 1299<p>An error will be thrown if an invalid address is provided.</p> 1300<p>The <code>dns.setServers()</code> method must not be called while a DNS query is in 1301progress.</p> 1302<p>The <a href="#dnssetserversservers"><code>dns.setServers()</code></a> method affects only <a href="#dnsresolvehostname-rrtype-callback"><code>dns.resolve()</code></a>, 1303<code>dns.resolve*()</code> and <a href="#dnsreverseip-callback"><code>dns.reverse()</code></a> (and specifically <em>not</em> 1304<a href="#dnslookuphostname-options-callback"><code>dns.lookup()</code></a>).</p> 1305<p>This method works much like 1306<a href="https://man7.org/linux/man-pages/man5/resolv.conf.5.html">resolve.conf</a>. 1307That is, if attempting to resolve with the first server provided results in a 1308<code>NOTFOUND</code> error, the <code>resolve()</code> method will <em>not</em> attempt to resolve with 1309subsequent servers provided. Fallback DNS servers will only be used if the 1310earlier ones time out or result in some other error.</p> 1311</section><section><h3>DNS promises API<span><a class="mark" href="#dns-promises-api" id="dns-promises-api">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_promises_api"></a></h3> 1312<div class="api_metadata"> 1313<details class="changelog"><summary>History</summary> 1314<table> 1315<tbody><tr><th>Version</th><th>Changes</th></tr> 1316<tr><td>v15.0.0</td> 1317<td><p>Exposed as <code>require('dns/promises')</code>.</p></td></tr> 1318<tr><td>v11.14.0, v10.17.0</td> 1319<td><p>This API is no longer experimental.</p></td></tr> 1320<tr><td>v10.6.0</td> 1321<td><p><span>Added in: v10.6.0</span></p></td></tr> 1322</tbody></table> 1323</details> 1324</div> 1325<p>The <code>dns.promises</code> API provides an alternative set of asynchronous DNS methods 1326that return <code>Promise</code> objects rather than using callbacks. The API is accessible 1327via <code>require('node:dns').promises</code> or <code>require('node:dns/promises')</code>.</p> 1328<h4>Class: <code>dnsPromises.Resolver</code><span><a class="mark" href="#class-dnspromisesresolver" id="class-dnspromisesresolver">#</a></span><a aria-hidden="true" class="legacy" id="dns_class_dnspromises_resolver"></a></h4> 1329<div class="api_metadata"> 1330<span>Added in: v10.6.0</span> 1331</div> 1332<p>An independent resolver for DNS requests.</p> 1333<p>Creating a new resolver uses the default server settings. Setting 1334the servers used for a resolver using 1335<a href="#dnspromisessetserversservers"><code>resolver.setServers()</code></a> does not affect 1336other resolvers:</p> 1337<pre><code class="language-js"><span class="hljs-keyword">const</span> { <span class="hljs-title class_">Resolver</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:dns'</span>).<span class="hljs-property">promises</span>; 1338<span class="hljs-keyword">const</span> resolver = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Resolver</span>(); 1339resolver.<span class="hljs-title function_">setServers</span>([<span class="hljs-string">'4.4.4.4'</span>]); 1340 1341<span class="hljs-comment">// This request will use the server at 4.4.4.4, independent of global settings.</span> 1342resolver.<span class="hljs-title function_">resolve4</span>(<span class="hljs-string">'example.org'</span>).<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">addresses</span>) =></span> { 1343 <span class="hljs-comment">// ...</span> 1344}); 1345 1346<span class="hljs-comment">// Alternatively, the same code can be written using async-await style.</span> 1347(<span class="hljs-keyword">async</span> <span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) { 1348 <span class="hljs-keyword">const</span> addresses = <span class="hljs-keyword">await</span> resolver.<span class="hljs-title function_">resolve4</span>(<span class="hljs-string">'example.org'</span>); 1349})();</code> <button class="copy-button">copy</button></pre> 1350<p>The following methods from the <code>dnsPromises</code> API are available:</p> 1351<ul> 1352<li><a href="#dnspromisesgetservers"><code>resolver.getServers()</code></a></li> 1353<li><a href="#dnspromisesresolvehostname-rrtype"><code>resolver.resolve()</code></a></li> 1354<li><a href="#dnspromisesresolve4hostname-options"><code>resolver.resolve4()</code></a></li> 1355<li><a href="#dnspromisesresolve6hostname-options"><code>resolver.resolve6()</code></a></li> 1356<li><a href="#dnspromisesresolveanyhostname"><code>resolver.resolveAny()</code></a></li> 1357<li><a href="#dnspromisesresolvecaahostname"><code>resolver.resolveCaa()</code></a></li> 1358<li><a href="#dnspromisesresolvecnamehostname"><code>resolver.resolveCname()</code></a></li> 1359<li><a href="#dnspromisesresolvemxhostname"><code>resolver.resolveMx()</code></a></li> 1360<li><a href="#dnspromisesresolvenaptrhostname"><code>resolver.resolveNaptr()</code></a></li> 1361<li><a href="#dnspromisesresolvenshostname"><code>resolver.resolveNs()</code></a></li> 1362<li><a href="#dnspromisesresolveptrhostname"><code>resolver.resolvePtr()</code></a></li> 1363<li><a href="#dnspromisesresolvesoahostname"><code>resolver.resolveSoa()</code></a></li> 1364<li><a href="#dnspromisesresolvesrvhostname"><code>resolver.resolveSrv()</code></a></li> 1365<li><a href="#dnspromisesresolvetxthostname"><code>resolver.resolveTxt()</code></a></li> 1366<li><a href="#dnspromisesreverseip"><code>resolver.reverse()</code></a></li> 1367<li><a href="#dnspromisessetserversservers"><code>resolver.setServers()</code></a></li> 1368</ul> 1369<h4><code>resolver.cancel()</code><span><a class="mark" href="#resolvercancel_1" id="resolvercancel_1">#</a></span><a aria-hidden="true" class="legacy" id="dns_resolver_cancel_1"></a></h4> 1370<div class="api_metadata"> 1371<span>Added in: v15.3.0, v14.17.0</span> 1372</div> 1373<p>Cancel all outstanding DNS queries made by this resolver. The corresponding 1374promises will be rejected with an error with the code <code>ECANCELLED</code>.</p> 1375<h4><code>dnsPromises.getServers()</code><span><a class="mark" href="#dnspromisesgetservers" id="dnspromisesgetservers">#</a></span><a aria-hidden="true" class="legacy" id="dns_dnspromises_getservers"></a></h4> 1376<div class="api_metadata"> 1377<span>Added in: v10.6.0</span> 1378</div> 1379<ul> 1380<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li> 1381</ul> 1382<p>Returns an array of IP address strings, formatted according to <a href="https://tools.ietf.org/html/rfc5952#section-6">RFC 5952</a>, 1383that are currently configured for DNS resolution. A string will include a port 1384section if a custom port is used.</p> 1385<!-- eslint-disable semi--> 1386<pre><code class="language-js">[ 1387 <span class="hljs-string">'4.4.4.4'</span>, 1388 <span class="hljs-string">'2001:4860:4860::8888'</span>, 1389 <span class="hljs-string">'4.4.4.4:1053'</span>, 1390 <span class="hljs-string">'[2001:4860:4860::8888]:1053'</span>, 1391]</code> <button class="copy-button">copy</button></pre> 1392<h4><code>dnsPromises.lookup(hostname[, options])</code><span><a class="mark" href="#dnspromiseslookuphostname-options" id="dnspromiseslookuphostname-options">#</a></span><a aria-hidden="true" class="legacy" id="dns_dnspromises_lookup_hostname_options"></a></h4> 1393<div class="api_metadata"> 1394<span>Added in: v10.6.0</span> 1395</div> 1396<ul> 1397<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1398<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1399<ul> 1400<li><code>family</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The record family. Must be <code>4</code>, <code>6</code>, or <code>0</code>. The value 1401<code>0</code> indicates that IPv4 and IPv6 addresses are both returned. <strong>Default:</strong> 1402<code>0</code>.</li> 1403<li><code>hints</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> One or more <a href="#supported-getaddrinfo-flags">supported <code>getaddrinfo</code> flags</a>. Multiple 1404flags may be passed by bitwise <code>OR</code>ing their values.</li> 1405<li><code>all</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, the <code>Promise</code> is resolved with all addresses in 1406an array. Otherwise, returns a single address. <strong>Default:</strong> <code>false</code>.</li> 1407<li><code>verbatim</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, the <code>Promise</code> is resolved with IPv4 and 1408IPv6 addresses in the order the DNS resolver returned them. When <code>false</code>, 1409IPv4 addresses are placed before IPv6 addresses. 1410<strong>Default:</strong> currently <code>false</code> (addresses are reordered) but this is 1411expected to change in the not too distant future. Default value is 1412configurable using <a href="#dnssetdefaultresultorderorder"><code>dns.setDefaultResultOrder()</code></a> or 1413<a href="cli.html#--dns-result-orderorder"><code>--dns-result-order</code></a>. New code should use <code>{ verbatim: true }</code>.</li> 1414</ul> 1415</li> 1416</ul> 1417<p>Resolves a host name (e.g. <code>'nodejs.org'</code>) into the first found A (IPv4) or 1418AAAA (IPv6) record. All <code>option</code> properties are optional. If <code>options</code> is an 1419integer, then it must be <code>4</code> or <code>6</code> – if <code>options</code> is not provided, then IPv4 1420and IPv6 addresses are both returned if found.</p> 1421<p>With the <code>all</code> option set to <code>true</code>, the <code>Promise</code> is resolved with <code>addresses</code> 1422being an array of objects with the properties <code>address</code> and <code>family</code>.</p> 1423<p>On error, the <code>Promise</code> is rejected with an <a href="errors.html#class-error"><code>Error</code></a> object, where <code>err.code</code> 1424is the error code. 1425Keep in mind that <code>err.code</code> will be set to <code>'ENOTFOUND'</code> not only when 1426the host name does not exist but also when the lookup fails in other ways 1427such as no available file descriptors.</p> 1428<p><a href="#dnspromiseslookuphostname-options"><code>dnsPromises.lookup()</code></a> does not necessarily have anything to do with the DNS 1429protocol. The implementation uses an operating system facility that can 1430associate names with addresses and vice versa. This implementation can have 1431subtle but important consequences on the behavior of any Node.js program. Please 1432take some time to consult the <a href="#implementation-considerations">Implementation considerations section</a> before 1433using <code>dnsPromises.lookup()</code>.</p> 1434<p>Example usage:</p> 1435<pre><code class="language-js"><span class="hljs-keyword">const</span> dns = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:dns'</span>); 1436<span class="hljs-keyword">const</span> dnsPromises = dns.<span class="hljs-property">promises</span>; 1437<span class="hljs-keyword">const</span> options = { 1438 <span class="hljs-attr">family</span>: <span class="hljs-number">6</span>, 1439 <span class="hljs-attr">hints</span>: dns.<span class="hljs-property">ADDRCONFIG</span> | dns.<span class="hljs-property">V4MAPPED</span>, 1440}; 1441 1442dnsPromises.<span class="hljs-title function_">lookup</span>(<span class="hljs-string">'example.com'</span>, options).<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">result</span>) =></span> { 1443 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'address: %j family: IPv%s'</span>, result.<span class="hljs-property">address</span>, result.<span class="hljs-property">family</span>); 1444 <span class="hljs-comment">// address: "2606:2800:220:1:248:1893:25c8:1946" family: IPv6</span> 1445}); 1446 1447<span class="hljs-comment">// When options.all is true, the result will be an Array.</span> 1448options.<span class="hljs-property">all</span> = <span class="hljs-literal">true</span>; 1449dnsPromises.<span class="hljs-title function_">lookup</span>(<span class="hljs-string">'example.com'</span>, options).<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">result</span>) =></span> { 1450 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'addresses: %j'</span>, result); 1451 <span class="hljs-comment">// addresses: [{"address":"2606:2800:220:1:248:1893:25c8:1946","family":6}]</span> 1452});</code> <button class="copy-button">copy</button></pre> 1453<h4><code>dnsPromises.lookupService(address, port)</code><span><a class="mark" href="#dnspromiseslookupserviceaddress-port" id="dnspromiseslookupserviceaddress-port">#</a></span><a aria-hidden="true" class="legacy" id="dns_dnspromises_lookupservice_address_port"></a></h4> 1454<div class="api_metadata"> 1455<span>Added in: v10.6.0</span> 1456</div> 1457<ul> 1458<li><code>address</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1459<li><code>port</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1460</ul> 1461<p>Resolves the given <code>address</code> and <code>port</code> into a host name and service using 1462the operating system's underlying <code>getnameinfo</code> implementation.</p> 1463<p>If <code>address</code> is not a valid IP address, a <code>TypeError</code> will be thrown. 1464The <code>port</code> will be coerced to a number. If it is not a legal port, a <code>TypeError</code> 1465will be thrown.</p> 1466<p>On error, the <code>Promise</code> is rejected with an <a href="errors.html#class-error"><code>Error</code></a> object, where <code>err.code</code> 1467is the error code.</p> 1468<pre><code class="language-js"><span class="hljs-keyword">const</span> dnsPromises = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:dns'</span>).<span class="hljs-property">promises</span>; 1469dnsPromises.<span class="hljs-title function_">lookupService</span>(<span class="hljs-string">'127.0.0.1'</span>, <span class="hljs-number">22</span>).<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">result</span>) =></span> { 1470 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(result.<span class="hljs-property">hostname</span>, result.<span class="hljs-property">service</span>); 1471 <span class="hljs-comment">// Prints: localhost ssh</span> 1472});</code> <button class="copy-button">copy</button></pre> 1473<h4><code>dnsPromises.resolve(hostname[, rrtype])</code><span><a class="mark" href="#dnspromisesresolvehostname-rrtype" id="dnspromisesresolvehostname-rrtype">#</a></span><a aria-hidden="true" class="legacy" id="dns_dnspromises_resolve_hostname_rrtype"></a></h4> 1474<div class="api_metadata"> 1475<span>Added in: v10.6.0</span> 1476</div> 1477<ul> 1478<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Host name to resolve.</li> 1479<li><code>rrtype</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Resource record type. <strong>Default:</strong> <code>'A'</code>.</li> 1480</ul> 1481<p>Uses the DNS protocol to resolve a host name (e.g. <code>'nodejs.org'</code>) into an array 1482of the resource records. When successful, the <code>Promise</code> is resolved with an 1483array of resource records. The type and structure of individual results vary 1484based on <code>rrtype</code>:</p> 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568<table><thead><tr><th><code>rrtype</code></th><th><code>records</code> contains</th><th>Result type</th><th>Shorthand method</th></tr></thead><tbody><tr><td><code>'A'</code></td><td>IPv4 addresses (default)</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></td><td><a href="#dnspromisesresolve4hostname-options"><code>dnsPromises.resolve4()</code></a></td></tr><tr><td><code>'AAAA'</code></td><td>IPv6 addresses</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></td><td><a href="#dnspromisesresolve6hostname-options"><code>dnsPromises.resolve6()</code></a></td></tr><tr><td><code>'ANY'</code></td><td>any records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dnspromisesresolveanyhostname"><code>dnsPromises.resolveAny()</code></a></td></tr><tr><td><code>'CAA'</code></td><td>CA authorization records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dnspromisesresolvecaahostname"><code>dnsPromises.resolveCaa()</code></a></td></tr><tr><td><code>'CNAME'</code></td><td>canonical name records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></td><td><a href="#dnspromisesresolvecnamehostname"><code>dnsPromises.resolveCname()</code></a></td></tr><tr><td><code>'MX'</code></td><td>mail exchange records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dnspromisesresolvemxhostname"><code>dnsPromises.resolveMx()</code></a></td></tr><tr><td><code>'NAPTR'</code></td><td>name authority pointer records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dnspromisesresolvenaptrhostname"><code>dnsPromises.resolveNaptr()</code></a></td></tr><tr><td><code>'NS'</code></td><td>name server records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></td><td><a href="#dnspromisesresolvenshostname"><code>dnsPromises.resolveNs()</code></a></td></tr><tr><td><code>'PTR'</code></td><td>pointer records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></td><td><a href="#dnspromisesresolveptrhostname"><code>dnsPromises.resolvePtr()</code></a></td></tr><tr><td><code>'SOA'</code></td><td>start of authority records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dnspromisesresolvesoahostname"><code>dnsPromises.resolveSoa()</code></a></td></tr><tr><td><code>'SRV'</code></td><td>service records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></td><td><a href="#dnspromisesresolvesrvhostname"><code>dnsPromises.resolveSrv()</code></a></td></tr><tr><td><code>'TXT'</code></td><td>text records</td><td><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></td><td><a href="#dnspromisesresolvetxthostname"><code>dnsPromises.resolveTxt()</code></a></td></tr></tbody></table> 1569<p>On error, the <code>Promise</code> is rejected with an <a href="errors.html#class-error"><code>Error</code></a> object, where <code>err.code</code> 1570is one of the <a href="#error-codes">DNS error codes</a>.</p> 1571<h4><code>dnsPromises.resolve4(hostname[, options])</code><span><a class="mark" href="#dnspromisesresolve4hostname-options" id="dnspromisesresolve4hostname-options">#</a></span><a aria-hidden="true" class="legacy" id="dns_dnspromises_resolve4_hostname_options"></a></h4> 1572<div class="api_metadata"> 1573<span>Added in: v10.6.0</span> 1574</div> 1575<ul> 1576<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Host name to resolve.</li> 1577<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1578<ul> 1579<li><code>ttl</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Retrieve the Time-To-Live value (TTL) of each record. 1580When <code>true</code>, the <code>Promise</code> is resolved with an array of 1581<code>{ address: '1.2.3.4', ttl: 60 }</code> objects rather than an array of strings, 1582with the TTL expressed in seconds.</li> 1583</ul> 1584</li> 1585</ul> 1586<p>Uses the DNS protocol to resolve IPv4 addresses (<code>A</code> records) for the 1587<code>hostname</code>. On success, the <code>Promise</code> is resolved with an array of IPv4 1588addresses (e.g. <code>['74.125.79.104', '74.125.79.105', '74.125.79.106']</code>).</p> 1589<h4><code>dnsPromises.resolve6(hostname[, options])</code><span><a class="mark" href="#dnspromisesresolve6hostname-options" id="dnspromisesresolve6hostname-options">#</a></span><a aria-hidden="true" class="legacy" id="dns_dnspromises_resolve6_hostname_options"></a></h4> 1590<div class="api_metadata"> 1591<span>Added in: v10.6.0</span> 1592</div> 1593<ul> 1594<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Host name to resolve.</li> 1595<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1596<ul> 1597<li><code>ttl</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Retrieve the Time-To-Live value (TTL) of each record. 1598When <code>true</code>, the <code>Promise</code> is resolved with an array of 1599<code>{ address: '0:1:2:3:4:5:6:7', ttl: 60 }</code> objects rather than an array of 1600strings, with the TTL expressed in seconds.</li> 1601</ul> 1602</li> 1603</ul> 1604<p>Uses the DNS protocol to resolve IPv6 addresses (<code>AAAA</code> records) for the 1605<code>hostname</code>. On success, the <code>Promise</code> is resolved with an array of IPv6 1606addresses.</p> 1607<h4><code>dnsPromises.resolveAny(hostname)</code><span><a class="mark" href="#dnspromisesresolveanyhostname" id="dnspromisesresolveanyhostname">#</a></span><a aria-hidden="true" class="legacy" id="dns_dnspromises_resolveany_hostname"></a></h4> 1608<div class="api_metadata"> 1609<span>Added in: v10.6.0</span> 1610</div> 1611<ul> 1612<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1613</ul> 1614<p>Uses the DNS protocol to resolve all records (also known as <code>ANY</code> or <code>*</code> query). 1615On success, the <code>Promise</code> is resolved with an array containing various types of 1616records. Each object has a property <code>type</code> that indicates the type of the 1617current record. And depending on the <code>type</code>, additional properties will be 1618present on the object:</p> 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668<table><thead><tr><th>Type</th><th>Properties</th></tr></thead><tbody><tr><td><code>'A'</code></td><td><code>address</code>/<code>ttl</code></td></tr><tr><td><code>'AAAA'</code></td><td><code>address</code>/<code>ttl</code></td></tr><tr><td><code>'CNAME'</code></td><td><code>value</code></td></tr><tr><td><code>'MX'</code></td><td>Refer to <a href="#dnspromisesresolvemxhostname"><code>dnsPromises.resolveMx()</code></a></td></tr><tr><td><code>'NAPTR'</code></td><td>Refer to <a href="#dnspromisesresolvenaptrhostname"><code>dnsPromises.resolveNaptr()</code></a></td></tr><tr><td><code>'NS'</code></td><td><code>value</code></td></tr><tr><td><code>'PTR'</code></td><td><code>value</code></td></tr><tr><td><code>'SOA'</code></td><td>Refer to <a href="#dnspromisesresolvesoahostname"><code>dnsPromises.resolveSoa()</code></a></td></tr><tr><td><code>'SRV'</code></td><td>Refer to <a href="#dnspromisesresolvesrvhostname"><code>dnsPromises.resolveSrv()</code></a></td></tr><tr><td><code>'TXT'</code></td><td>This type of record contains an array property called <code>entries</code> which refers to <a href="#dnspromisesresolvetxthostname"><code>dnsPromises.resolveTxt()</code></a>, e.g. <code>{ entries: ['...'], type: 'TXT' }</code></td></tr></tbody></table> 1669<p>Here is an example of the result object:</p> 1670<!-- eslint-disable semi --> 1671<pre><code class="language-js">[ { <span class="hljs-attr">type</span>: <span class="hljs-string">'A'</span>, <span class="hljs-attr">address</span>: <span class="hljs-string">'127.0.0.1'</span>, <span class="hljs-attr">ttl</span>: <span class="hljs-number">299</span> }, 1672 { <span class="hljs-attr">type</span>: <span class="hljs-string">'CNAME'</span>, <span class="hljs-attr">value</span>: <span class="hljs-string">'example.com'</span> }, 1673 { <span class="hljs-attr">type</span>: <span class="hljs-string">'MX'</span>, <span class="hljs-attr">exchange</span>: <span class="hljs-string">'alt4.aspmx.l.example.com'</span>, <span class="hljs-attr">priority</span>: <span class="hljs-number">50</span> }, 1674 { <span class="hljs-attr">type</span>: <span class="hljs-string">'NS'</span>, <span class="hljs-attr">value</span>: <span class="hljs-string">'ns1.example.com'</span> }, 1675 { <span class="hljs-attr">type</span>: <span class="hljs-string">'TXT'</span>, <span class="hljs-attr">entries</span>: [ <span class="hljs-string">'v=spf1 include:_spf.example.com ~all'</span> ] }, 1676 { <span class="hljs-attr">type</span>: <span class="hljs-string">'SOA'</span>, 1677 <span class="hljs-attr">nsname</span>: <span class="hljs-string">'ns1.example.com'</span>, 1678 <span class="hljs-attr">hostmaster</span>: <span class="hljs-string">'admin.example.com'</span>, 1679 <span class="hljs-attr">serial</span>: <span class="hljs-number">156696742</span>, 1680 <span class="hljs-attr">refresh</span>: <span class="hljs-number">900</span>, 1681 <span class="hljs-attr">retry</span>: <span class="hljs-number">900</span>, 1682 <span class="hljs-attr">expire</span>: <span class="hljs-number">1800</span>, 1683 <span class="hljs-attr">minttl</span>: <span class="hljs-number">60</span> } ]</code> <button class="copy-button">copy</button></pre> 1684<h4><code>dnsPromises.resolveCaa(hostname)</code><span><a class="mark" href="#dnspromisesresolvecaahostname" id="dnspromisesresolvecaahostname">#</a></span><a aria-hidden="true" class="legacy" id="dns_dnspromises_resolvecaa_hostname"></a></h4> 1685<div class="api_metadata"> 1686<span>Added in: v15.0.0, v14.17.0</span> 1687</div> 1688<ul> 1689<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1690</ul> 1691<p>Uses the DNS protocol to resolve <code>CAA</code> records for the <code>hostname</code>. On success, 1692the <code>Promise</code> is resolved with an array of objects containing available 1693certification authority authorization records available for the <code>hostname</code> 1694(e.g. <code>[{critical: 0, iodef: 'mailto:pki@example.com'},{critical: 128, issue: 'pki.example.com'}]</code>).</p> 1695<h4><code>dnsPromises.resolveCname(hostname)</code><span><a class="mark" href="#dnspromisesresolvecnamehostname" id="dnspromisesresolvecnamehostname">#</a></span><a aria-hidden="true" class="legacy" id="dns_dnspromises_resolvecname_hostname"></a></h4> 1696<div class="api_metadata"> 1697<span>Added in: v10.6.0</span> 1698</div> 1699<ul> 1700<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1701</ul> 1702<p>Uses the DNS protocol to resolve <code>CNAME</code> records for the <code>hostname</code>. On success, 1703the <code>Promise</code> is resolved with an array of canonical name records available for 1704the <code>hostname</code> (e.g. <code>['bar.example.com']</code>).</p> 1705<h4><code>dnsPromises.resolveMx(hostname)</code><span><a class="mark" href="#dnspromisesresolvemxhostname" id="dnspromisesresolvemxhostname">#</a></span><a aria-hidden="true" class="legacy" id="dns_dnspromises_resolvemx_hostname"></a></h4> 1706<div class="api_metadata"> 1707<span>Added in: v10.6.0</span> 1708</div> 1709<ul> 1710<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1711</ul> 1712<p>Uses the DNS protocol to resolve mail exchange records (<code>MX</code> records) for the 1713<code>hostname</code>. On success, the <code>Promise</code> is resolved with an array of objects 1714containing both a <code>priority</code> and <code>exchange</code> property (e.g. 1715<code>[{priority: 10, exchange: 'mx.example.com'}, ...]</code>).</p> 1716<h4><code>dnsPromises.resolveNaptr(hostname)</code><span><a class="mark" href="#dnspromisesresolvenaptrhostname" id="dnspromisesresolvenaptrhostname">#</a></span><a aria-hidden="true" class="legacy" id="dns_dnspromises_resolvenaptr_hostname"></a></h4> 1717<div class="api_metadata"> 1718<span>Added in: v10.6.0</span> 1719</div> 1720<ul> 1721<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1722</ul> 1723<p>Uses the DNS protocol to resolve regular expression-based records (<code>NAPTR</code> 1724records) for the <code>hostname</code>. On success, the <code>Promise</code> is resolved with an array 1725of objects with the following properties:</p> 1726<ul> 1727<li><code>flags</code></li> 1728<li><code>service</code></li> 1729<li><code>regexp</code></li> 1730<li><code>replacement</code></li> 1731<li><code>order</code></li> 1732<li><code>preference</code></li> 1733</ul> 1734<!-- eslint-skip --> 1735<pre><code class="language-js">{ 1736 <span class="hljs-attr">flags</span>: <span class="hljs-string">'s'</span>, 1737 <span class="hljs-attr">service</span>: <span class="hljs-string">'SIP+D2U'</span>, 1738 <span class="hljs-attr">regexp</span>: <span class="hljs-string">''</span>, 1739 <span class="hljs-attr">replacement</span>: <span class="hljs-string">'_sip._udp.example.com'</span>, 1740 <span class="hljs-attr">order</span>: <span class="hljs-number">30</span>, 1741 <span class="hljs-attr">preference</span>: <span class="hljs-number">100</span> 1742}</code> <button class="copy-button">copy</button></pre> 1743<h4><code>dnsPromises.resolveNs(hostname)</code><span><a class="mark" href="#dnspromisesresolvenshostname" id="dnspromisesresolvenshostname">#</a></span><a aria-hidden="true" class="legacy" id="dns_dnspromises_resolvens_hostname"></a></h4> 1744<div class="api_metadata"> 1745<span>Added in: v10.6.0</span> 1746</div> 1747<ul> 1748<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1749</ul> 1750<p>Uses the DNS protocol to resolve name server records (<code>NS</code> records) for the 1751<code>hostname</code>. On success, the <code>Promise</code> is resolved with an array of name server 1752records available for <code>hostname</code> (e.g. 1753<code>['ns1.example.com', 'ns2.example.com']</code>).</p> 1754<h4><code>dnsPromises.resolvePtr(hostname)</code><span><a class="mark" href="#dnspromisesresolveptrhostname" id="dnspromisesresolveptrhostname">#</a></span><a aria-hidden="true" class="legacy" id="dns_dnspromises_resolveptr_hostname"></a></h4> 1755<div class="api_metadata"> 1756<span>Added in: v10.6.0</span> 1757</div> 1758<ul> 1759<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1760</ul> 1761<p>Uses the DNS protocol to resolve pointer records (<code>PTR</code> records) for the 1762<code>hostname</code>. On success, the <code>Promise</code> is resolved with an array of strings 1763containing the reply records.</p> 1764<h4><code>dnsPromises.resolveSoa(hostname)</code><span><a class="mark" href="#dnspromisesresolvesoahostname" id="dnspromisesresolvesoahostname">#</a></span><a aria-hidden="true" class="legacy" id="dns_dnspromises_resolvesoa_hostname"></a></h4> 1765<div class="api_metadata"> 1766<span>Added in: v10.6.0</span> 1767</div> 1768<ul> 1769<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1770</ul> 1771<p>Uses the DNS protocol to resolve a start of authority record (<code>SOA</code> record) for 1772the <code>hostname</code>. On success, the <code>Promise</code> is resolved with an object with the 1773following properties:</p> 1774<ul> 1775<li><code>nsname</code></li> 1776<li><code>hostmaster</code></li> 1777<li><code>serial</code></li> 1778<li><code>refresh</code></li> 1779<li><code>retry</code></li> 1780<li><code>expire</code></li> 1781<li><code>minttl</code></li> 1782</ul> 1783<!-- eslint-skip --> 1784<pre><code class="language-js">{ 1785 <span class="hljs-attr">nsname</span>: <span class="hljs-string">'ns.example.com'</span>, 1786 <span class="hljs-attr">hostmaster</span>: <span class="hljs-string">'root.example.com'</span>, 1787 <span class="hljs-attr">serial</span>: <span class="hljs-number">2013101809</span>, 1788 <span class="hljs-attr">refresh</span>: <span class="hljs-number">10000</span>, 1789 <span class="hljs-attr">retry</span>: <span class="hljs-number">2400</span>, 1790 <span class="hljs-attr">expire</span>: <span class="hljs-number">604800</span>, 1791 <span class="hljs-attr">minttl</span>: <span class="hljs-number">3600</span> 1792}</code> <button class="copy-button">copy</button></pre> 1793<h4><code>dnsPromises.resolveSrv(hostname)</code><span><a class="mark" href="#dnspromisesresolvesrvhostname" id="dnspromisesresolvesrvhostname">#</a></span><a aria-hidden="true" class="legacy" id="dns_dnspromises_resolvesrv_hostname"></a></h4> 1794<div class="api_metadata"> 1795<span>Added in: v10.6.0</span> 1796</div> 1797<ul> 1798<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1799</ul> 1800<p>Uses the DNS protocol to resolve service records (<code>SRV</code> records) for the 1801<code>hostname</code>. On success, the <code>Promise</code> is resolved with an array of objects with 1802the following properties:</p> 1803<ul> 1804<li><code>priority</code></li> 1805<li><code>weight</code></li> 1806<li><code>port</code></li> 1807<li><code>name</code></li> 1808</ul> 1809<!-- eslint-skip --> 1810<pre><code class="language-js">{ 1811 <span class="hljs-attr">priority</span>: <span class="hljs-number">10</span>, 1812 <span class="hljs-attr">weight</span>: <span class="hljs-number">5</span>, 1813 <span class="hljs-attr">port</span>: <span class="hljs-number">21223</span>, 1814 <span class="hljs-attr">name</span>: <span class="hljs-string">'service.example.com'</span> 1815}</code> <button class="copy-button">copy</button></pre> 1816<h4><code>dnsPromises.resolveTxt(hostname)</code><span><a class="mark" href="#dnspromisesresolvetxthostname" id="dnspromisesresolvetxthostname">#</a></span><a aria-hidden="true" class="legacy" id="dns_dnspromises_resolvetxt_hostname"></a></h4> 1817<div class="api_metadata"> 1818<span>Added in: v10.6.0</span> 1819</div> 1820<ul> 1821<li><code>hostname</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1822</ul> 1823<p>Uses the DNS protocol to resolve text queries (<code>TXT</code> records) for the 1824<code>hostname</code>. On success, the <code>Promise</code> is resolved with a two-dimensional array 1825of the text records available for <code>hostname</code> (e.g. 1826<code>[ ['v=spf1 ip4:0.0.0.0 ', '~all' ] ]</code>). Each sub-array contains TXT chunks of 1827one record. Depending on the use case, these could be either joined together or 1828treated separately.</p> 1829<h4><code>dnsPromises.reverse(ip)</code><span><a class="mark" href="#dnspromisesreverseip" id="dnspromisesreverseip">#</a></span><a aria-hidden="true" class="legacy" id="dns_dnspromises_reverse_ip"></a></h4> 1830<div class="api_metadata"> 1831<span>Added in: v10.6.0</span> 1832</div> 1833<ul> 1834<li><code>ip</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1835</ul> 1836<p>Performs a reverse DNS query that resolves an IPv4 or IPv6 address to an 1837array of host names.</p> 1838<p>On error, the <code>Promise</code> is rejected with an <a href="errors.html#class-error"><code>Error</code></a> object, where <code>err.code</code> 1839is one of the <a href="#error-codes">DNS error codes</a>.</p> 1840<h4><code>dnsPromises.setDefaultResultOrder(order)</code><span><a class="mark" href="#dnspromisessetdefaultresultorderorder" id="dnspromisessetdefaultresultorderorder">#</a></span><a aria-hidden="true" class="legacy" id="dns_dnspromises_setdefaultresultorder_order"></a></h4> 1841<div class="api_metadata"> 1842<details class="changelog"><summary>History</summary> 1843<table> 1844<tbody><tr><th>Version</th><th>Changes</th></tr> 1845<tr><td>v17.0.0</td> 1846<td><p>Changed default value to <code>verbatim</code>.</p></td></tr> 1847<tr><td>v16.4.0, v14.18.0</td> 1848<td><p><span>Added in: v16.4.0, v14.18.0</span></p></td></tr> 1849</tbody></table> 1850</details> 1851</div> 1852<ul> 1853<li><code>order</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> must be <code>'ipv4first'</code> or <code>'verbatim'</code>.</li> 1854</ul> 1855<p>Set the default value of <code>verbatim</code> in <a href="#dnslookuphostname-options-callback"><code>dns.lookup()</code></a> and 1856<a href="#dnspromiseslookuphostname-options"><code>dnsPromises.lookup()</code></a>. The value could be:</p> 1857<ul> 1858<li><code>ipv4first</code>: sets default <code>verbatim</code> <code>false</code>.</li> 1859<li><code>verbatim</code>: sets default <code>verbatim</code> <code>true</code>.</li> 1860</ul> 1861<p>The default is <code>verbatim</code> and <a href="#dnspromisessetdefaultresultorderorder"><code>dnsPromises.setDefaultResultOrder()</code></a> have 1862higher priority than <a href="cli.html#--dns-result-orderorder"><code>--dns-result-order</code></a>. When using <a href="worker_threads.html">worker threads</a>, 1863<a href="#dnspromisessetdefaultresultorderorder"><code>dnsPromises.setDefaultResultOrder()</code></a> from the main thread won't affect the 1864default dns orders in workers.</p> 1865<h4><code>dnsPromises.getDefaultResultOrder()</code><span><a class="mark" href="#dnspromisesgetdefaultresultorder" id="dnspromisesgetdefaultresultorder">#</a></span><a aria-hidden="true" class="legacy" id="dns_dnspromises_getdefaultresultorder"></a></h4> 1866<div class="api_metadata"> 1867<span>Added in: v18.17.0</span> 1868</div> 1869<p>Get the value of <code>dnsOrder</code>.</p> 1870<h4><code>dnsPromises.setServers(servers)</code><span><a class="mark" href="#dnspromisessetserversservers" id="dnspromisessetserversservers">#</a></span><a aria-hidden="true" class="legacy" id="dns_dnspromises_setservers_servers"></a></h4> 1871<div class="api_metadata"> 1872<span>Added in: v10.6.0</span> 1873</div> 1874<ul> 1875<li><code>servers</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a> array of <a href="https://tools.ietf.org/html/rfc5952#section-6">RFC 5952</a> formatted addresses</li> 1876</ul> 1877<p>Sets the IP address and port of servers to be used when performing DNS 1878resolution. The <code>servers</code> argument is an array of <a href="https://tools.ietf.org/html/rfc5952#section-6">RFC 5952</a> formatted 1879addresses. If the port is the IANA default DNS port (53) it can be omitted.</p> 1880<pre><code class="language-js">dnsPromises.<span class="hljs-title function_">setServers</span>([ 1881 <span class="hljs-string">'4.4.4.4'</span>, 1882 <span class="hljs-string">'[2001:4860:4860::8888]'</span>, 1883 <span class="hljs-string">'4.4.4.4:1053'</span>, 1884 <span class="hljs-string">'[2001:4860:4860::8888]:1053'</span>, 1885]);</code> <button class="copy-button">copy</button></pre> 1886<p>An error will be thrown if an invalid address is provided.</p> 1887<p>The <code>dnsPromises.setServers()</code> method must not be called while a DNS query is in 1888progress.</p> 1889<p>This method works much like 1890<a href="https://man7.org/linux/man-pages/man5/resolv.conf.5.html">resolve.conf</a>. 1891That is, if attempting to resolve with the first server provided results in a 1892<code>NOTFOUND</code> error, the <code>resolve()</code> method will <em>not</em> attempt to resolve with 1893subsequent servers provided. Fallback DNS servers will only be used if the 1894earlier ones time out or result in some other error.</p> 1895</section><section><h3>Error codes<span><a class="mark" href="#error-codes" id="error-codes">#</a></span><a aria-hidden="true" class="legacy" id="dns_error_codes"></a></h3> 1896<p>Each DNS query can return one of the following error codes:</p> 1897<ul> 1898<li><code>dns.NODATA</code>: DNS server returned an answer with no data.</li> 1899<li><code>dns.FORMERR</code>: DNS server claims query was misformatted.</li> 1900<li><code>dns.SERVFAIL</code>: DNS server returned general failure.</li> 1901<li><code>dns.NOTFOUND</code>: Domain name not found.</li> 1902<li><code>dns.NOTIMP</code>: DNS server does not implement the requested operation.</li> 1903<li><code>dns.REFUSED</code>: DNS server refused query.</li> 1904<li><code>dns.BADQUERY</code>: Misformatted DNS query.</li> 1905<li><code>dns.BADNAME</code>: Misformatted host name.</li> 1906<li><code>dns.BADFAMILY</code>: Unsupported address family.</li> 1907<li><code>dns.BADRESP</code>: Misformatted DNS reply.</li> 1908<li><code>dns.CONNREFUSED</code>: Could not contact DNS servers.</li> 1909<li><code>dns.TIMEOUT</code>: Timeout while contacting DNS servers.</li> 1910<li><code>dns.EOF</code>: End of file.</li> 1911<li><code>dns.FILE</code>: Error reading file.</li> 1912<li><code>dns.NOMEM</code>: Out of memory.</li> 1913<li><code>dns.DESTRUCTION</code>: Channel is being destroyed.</li> 1914<li><code>dns.BADSTR</code>: Misformatted string.</li> 1915<li><code>dns.BADFLAGS</code>: Illegal flags specified.</li> 1916<li><code>dns.NONAME</code>: Given host name is not numeric.</li> 1917<li><code>dns.BADHINTS</code>: Illegal hints flags specified.</li> 1918<li><code>dns.NOTINITIALIZED</code>: c-ares library initialization not yet performed.</li> 1919<li><code>dns.LOADIPHLPAPI</code>: Error loading <code>iphlpapi.dll</code>.</li> 1920<li><code>dns.ADDRGETNETWORKPARAMS</code>: Could not find <code>GetNetworkParams</code> function.</li> 1921<li><code>dns.CANCELLED</code>: DNS query cancelled.</li> 1922</ul> 1923<p>The <code>dnsPromises</code> API also exports the above error codes, e.g., <code>dnsPromises.NODATA</code>.</p> 1924</section><section><h3>Implementation considerations<span><a class="mark" href="#implementation-considerations" id="implementation-considerations">#</a></span><a aria-hidden="true" class="legacy" id="dns_implementation_considerations"></a></h3> 1925<p>Although <a href="#dnslookuphostname-options-callback"><code>dns.lookup()</code></a> and the various <code>dns.resolve*()/dns.reverse()</code> 1926functions have the same goal of associating a network name with a network 1927address (or vice versa), their behavior is quite different. These differences 1928can have subtle but significant consequences on the behavior of Node.js 1929programs.</p> 1930<h4><code>dns.lookup()</code><span><a class="mark" href="#dnslookup" id="dnslookup">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_lookup"></a></h4> 1931<p>Under the hood, <a href="#dnslookuphostname-options-callback"><code>dns.lookup()</code></a> uses the same operating system facilities 1932as most other programs. For instance, <a href="#dnslookuphostname-options-callback"><code>dns.lookup()</code></a> will almost always 1933resolve a given name the same way as the <code>ping</code> command. On most POSIX-like 1934operating systems, the behavior of the <a href="#dnslookuphostname-options-callback"><code>dns.lookup()</code></a> function can be 1935modified by changing settings in <a href="http://man7.org/linux/man-pages/man5/nsswitch.conf.5.html"><code>nsswitch.conf(5)</code></a> and/or <a href="http://man7.org/linux/man-pages/man5/resolv.conf.5.html"><code>resolv.conf(5)</code></a>, 1936but changing these files will change the behavior of all other 1937programs running on the same operating system.</p> 1938<p>Though the call to <code>dns.lookup()</code> will be asynchronous from JavaScript's 1939perspective, it is implemented as a synchronous call to <a href="http://man7.org/linux/man-pages/man3/getaddrinfo.3.html"><code>getaddrinfo(3)</code></a> that runs 1940on libuv's threadpool. This can have surprising negative performance 1941implications for some applications, see the <a href="cli.html#uv_threadpool_sizesize"><code>UV_THREADPOOL_SIZE</code></a> 1942documentation for more information.</p> 1943<p>Various networking APIs will call <code>dns.lookup()</code> internally to resolve 1944host names. If that is an issue, consider resolving the host name to an address 1945using <code>dns.resolve()</code> and using the address instead of a host name. Also, some 1946networking APIs (such as <a href="net.html#socketconnectoptions-connectlistener"><code>socket.connect()</code></a> and <a href="dgram.html#dgramcreatesocketoptions-callback"><code>dgram.createSocket()</code></a>) 1947allow the default resolver, <code>dns.lookup()</code>, to be replaced.</p> 1948<h4><code>dns.resolve()</code>, <code>dns.resolve*()</code>, and <code>dns.reverse()</code><span><a class="mark" href="#dnsresolve-dnsresolve-and-dnsreverse" id="dnsresolve-dnsresolve-and-dnsreverse">#</a></span><a aria-hidden="true" class="legacy" id="dns_dns_resolve_dns_resolve_and_dns_reverse"></a></h4> 1949<p>These functions are implemented quite differently than <a href="#dnslookuphostname-options-callback"><code>dns.lookup()</code></a>. They 1950do not use <a href="http://man7.org/linux/man-pages/man3/getaddrinfo.3.html"><code>getaddrinfo(3)</code></a> and they <em>always</em> perform a DNS query on the 1951network. This network communication is always done asynchronously and does not 1952use libuv's threadpool.</p> 1953<p>As a result, these functions cannot have the same negative impact on other 1954processing that happens on libuv's threadpool that <a href="#dnslookuphostname-options-callback"><code>dns.lookup()</code></a> can have.</p> 1955<p>They do not use the same set of configuration files that <a href="#dnslookuphostname-options-callback"><code>dns.lookup()</code></a> 1956uses. For instance, they do not use the configuration from <code>/etc/hosts</code>.</p></section> 1957 <!-- API END --> 1958 </div> 1959 </div> 1960 </div> 1961</body> 1962</html> 1963