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href="#dgram_socket_addmembership_multicastaddress_multicastinterface"><code>socket.addMembership(multicastAddress[, multicastInterface])</code></a></li> 154<li><a href="#dgram_socket_addsourcespecificmembership_sourceaddress_groupaddress_multicastinterface"><code>socket.addSourceSpecificMembership(sourceAddress, groupAddress[, multicastInterface])</code></a></li> 155<li><a href="#dgram_socket_address"><code>socket.address()</code></a></li> 156<li><a href="#dgram_socket_bind_port_address_callback"><code>socket.bind([port][, address][, callback])</code></a></li> 157<li><a href="#dgram_socket_bind_options_callback"><code>socket.bind(options[, callback])</code></a></li> 158<li><a href="#dgram_socket_close_callback"><code>socket.close([callback])</code></a></li> 159<li><a href="#dgram_socket_connect_port_address_callback"><code>socket.connect(port[, address][, callback])</code></a></li> 160<li><a href="#dgram_socket_disconnect"><code>socket.disconnect()</code></a></li> 161<li><a href="#dgram_socket_dropmembership_multicastaddress_multicastinterface"><code>socket.dropMembership(multicastAddress[, multicastInterface])</code></a></li> 162<li><a href="#dgram_socket_dropsourcespecificmembership_sourceaddress_groupaddress_multicastinterface"><code>socket.dropSourceSpecificMembership(sourceAddress, groupAddress[, multicastInterface])</code></a></li> 163<li><a href="#dgram_socket_getrecvbuffersize"><code>socket.getRecvBufferSize()</code></a></li> 164<li><a href="#dgram_socket_getsendbuffersize"><code>socket.getSendBufferSize()</code></a></li> 165<li><a href="#dgram_socket_ref"><code>socket.ref()</code></a></li> 166<li><a href="#dgram_socket_remoteaddress"><code>socket.remoteAddress()</code></a></li> 167<li><a href="#dgram_socket_send_msg_offset_length_port_address_callback"><code>socket.send(msg[, offset, length][, port][, address][, callback])</code></a> 168<ul> 169<li><a href="#dgram_note_about_udp_datagram_size">Note about UDP datagram size</a></li> 170</ul> 171</li> 172<li><a href="#dgram_socket_setbroadcast_flag"><code>socket.setBroadcast(flag)</code></a></li> 173<li><a href="#dgram_socket_setmulticastinterface_multicastinterface"><code>socket.setMulticastInterface(multicastInterface)</code></a> 174<ul> 175<li><a href="#dgram_example_ipv6_outgoing_multicast_interface">Example: IPv6 outgoing multicast interface</a></li> 176<li><a href="#dgram_example_ipv4_outgoing_multicast_interface">Example: IPv4 outgoing multicast interface</a></li> 177<li><a href="#dgram_call_results">Call results</a></li> 178</ul> 179</li> 180<li><a href="#dgram_socket_setmulticastloopback_flag"><code>socket.setMulticastLoopback(flag)</code></a></li> 181<li><a href="#dgram_socket_setmulticastttl_ttl"><code>socket.setMulticastTTL(ttl)</code></a></li> 182<li><a href="#dgram_socket_setrecvbuffersize_size"><code>socket.setRecvBufferSize(size)</code></a></li> 183<li><a href="#dgram_socket_setsendbuffersize_size"><code>socket.setSendBufferSize(size)</code></a></li> 184<li><a href="#dgram_socket_setttl_ttl"><code>socket.setTTL(ttl)</code></a></li> 185<li><a href="#dgram_socket_unref"><code>socket.unref()</code></a></li> 186</ul> 187</li> 188<li><a href="#dgram_dgram_module_functions"><code>dgram</code> module functions</a> 189<ul> 190<li><a href="#dgram_dgram_createsocket_options_callback"><code>dgram.createSocket(options[, callback])</code></a></li> 191<li><a href="#dgram_dgram_createsocket_type_callback"><code>dgram.createSocket(type[, callback])</code></a></li> 192</ul> 193</li> 194</ul> 195</li> 196</ul></details> 197 198 <div id="apicontent"> 199 <h2>UDP/datagram sockets<span><a class="mark" href="#dgram_udp_datagram_sockets" id="dgram_udp_datagram_sockets">#</a></span></h2> 200 201<p></p><div class="api_stability api_stability_2"><a href="documentation.html#documentation_stability_index">Stability: 2</a> - Stable</div><p></p> 202 203<p><strong>Source Code:</strong> <a href="https://github.com/nodejs/node/blob/v14.19.1/lib/dgram.js">lib/dgram.js</a></p> 204<p>The <code>dgram</code> module provides an implementation of UDP datagram sockets.</p> 205<pre><code class="language-js"><span class="hljs-keyword">const</span> dgram = <span class="hljs-built_in">require</span>(<span class="hljs-string">'dgram'</span>); 206<span class="hljs-keyword">const</span> server = dgram.<span class="hljs-title function_">createSocket</span>(<span class="hljs-string">'udp4'</span>); 207 208server.<span class="hljs-title function_">on</span>(<span class="hljs-string">'error'</span>, <span class="hljs-function">(<span class="hljs-params">err</span>) =></span> { 209 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`server error:\n<span class="hljs-subst">${err.stack}</span>`</span>); 210 server.<span class="hljs-title function_">close</span>(); 211}); 212 213server.<span class="hljs-title function_">on</span>(<span class="hljs-string">'message'</span>, <span class="hljs-function">(<span class="hljs-params">msg, rinfo</span>) =></span> { 214 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`server got: <span class="hljs-subst">${msg}</span> from <span class="hljs-subst">${rinfo.address}</span>:<span class="hljs-subst">${rinfo.port}</span>`</span>); 215}); 216 217server.<span class="hljs-title function_">on</span>(<span class="hljs-string">'listening'</span>, <span class="hljs-function">() =></span> { 218 <span class="hljs-keyword">const</span> address = server.<span class="hljs-title function_">address</span>(); 219 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`server listening <span class="hljs-subst">${address.address}</span>:<span class="hljs-subst">${address.port}</span>`</span>); 220}); 221 222server.<span class="hljs-title function_">bind</span>(<span class="hljs-number">41234</span>); 223<span class="hljs-comment">// Prints: server listening 0.0.0.0:41234</span></code></pre> 224<section><h3>Class: <code>dgram.Socket</code><span><a class="mark" href="#dgram_class_dgram_socket" id="dgram_class_dgram_socket">#</a></span></h3> 225<div class="api_metadata"> 226<span>Added in: v0.1.99</span> 227</div> 228<ul> 229<li>Extends: <a href="events.html#events_class_eventemitter" class="type"><EventEmitter></a></li> 230</ul> 231<p>Encapsulates the datagram functionality.</p> 232<p>New instances of <code>dgram.Socket</code> are created using <a href="#dgram_dgram_createsocket_options_callback"><code>dgram.createSocket()</code></a>. 233The <code>new</code> keyword is not to be used to create <code>dgram.Socket</code> instances.</p> 234<h4>Event: <code>'close'</code><span><a class="mark" href="#dgram_event_close" id="dgram_event_close">#</a></span></h4> 235<div class="api_metadata"> 236<span>Added in: v0.1.99</span> 237</div> 238<p>The <code>'close'</code> event is emitted after a socket is closed with <a href="#dgram_socket_close_callback"><code>close()</code></a>. 239Once triggered, no new <code>'message'</code> events will be emitted on this socket.</p> 240<h4>Event: <code>'connect'</code><span><a class="mark" href="#dgram_event_connect" id="dgram_event_connect">#</a></span></h4> 241<div class="api_metadata"> 242<span>Added in: v12.0.0</span> 243</div> 244<p>The <code>'connect'</code> event is emitted after a socket is associated to a remote 245address as a result of a successful <a href="#dgram_socket_connect_port_address_callback"><code>connect()</code></a> call.</p> 246<h4>Event: <code>'error'</code><span><a class="mark" href="#dgram_event_error" id="dgram_event_error">#</a></span></h4> 247<div class="api_metadata"> 248<span>Added in: v0.1.99</span> 249</div> 250<ul> 251<li><code>exception</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 252</ul> 253<p>The <code>'error'</code> event is emitted whenever any error occurs. The event handler 254function is passed a single <code>Error</code> object.</p> 255<h4>Event: <code>'listening'</code><span><a class="mark" href="#dgram_event_listening" id="dgram_event_listening">#</a></span></h4> 256<div class="api_metadata"> 257<span>Added in: v0.1.99</span> 258</div> 259<p>The <code>'listening'</code> event is emitted once the <code>dgram.Socket</code> is addressable and 260can receive data. This happens either explicitly with <code>socket.bind()</code> or 261implicitly the first time data is sent using <code>socket.send()</code>. 262Until the <code>dgram.Socket</code> is listening, the underlying system resources do not 263exist and calls such as <code>socket.address()</code> and <code>socket.setTTL()</code> will fail.</p> 264<h4>Event: <code>'message'</code><span><a class="mark" href="#dgram_event_message" id="dgram_event_message">#</a></span></h4> 265<div class="api_metadata"> 266<span>Added in: v0.1.99</span> 267</div> 268<p>The <code>'message'</code> event is emitted when a new datagram is available on a socket. 269The event handler function is passed two arguments: <code>msg</code> and <code>rinfo</code>.</p> 270<ul> 271<li><code>msg</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> The message.</li> 272<li><code>rinfo</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Remote address information. 273<ul> 274<li><code>address</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The sender address.</li> 275<li><code>family</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The address family (<code>'IPv4'</code> or <code>'IPv6'</code>).</li> 276<li><code>port</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The sender port.</li> 277<li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The message size.</li> 278</ul> 279</li> 280</ul> 281<p>If the source address of the incoming packet is an IPv6 link-local 282address, the interface name is added to the <code>address</code>. For 283example, a packet received on the <code>en0</code> interface might have the 284address field set to <code>'fe80::2618:1234:ab11:3b9c%en0'</code>, where <code>'%en0'</code> 285is the interface name as a zone ID suffix.</p> 286<h4><code>socket.addMembership(multicastAddress[, multicastInterface])</code><span><a class="mark" href="#dgram_socket_addmembership_multicastaddress_multicastinterface" id="dgram_socket_addmembership_multicastaddress_multicastinterface">#</a></span></h4> 287<div class="api_metadata"> 288<span>Added in: v0.6.9</span> 289</div> 290<ul> 291<li><code>multicastAddress</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 292<li><code>multicastInterface</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 293</ul> 294<p>Tells the kernel to join a multicast group at the given <code>multicastAddress</code> and 295<code>multicastInterface</code> using the <code>IP_ADD_MEMBERSHIP</code> socket option. If the 296<code>multicastInterface</code> argument is not specified, the operating system will choose 297one interface and will add membership to it. To add membership to every 298available interface, call <code>addMembership</code> multiple times, once per interface.</p> 299<p>When called on an unbound socket, this method will implicitly bind to a random 300port, listening on all interfaces.</p> 301<p>When sharing a UDP socket across multiple <code>cluster</code> workers, the 302<code>socket.addMembership()</code> function must be called only once or an 303<code>EADDRINUSE</code> error will occur:</p> 304<pre><code class="language-js"><span class="hljs-keyword">const</span> cluster = <span class="hljs-built_in">require</span>(<span class="hljs-string">'cluster'</span>); 305<span class="hljs-keyword">const</span> dgram = <span class="hljs-built_in">require</span>(<span class="hljs-string">'dgram'</span>); 306<span class="hljs-keyword">if</span> (cluster.<span class="hljs-property">isMaster</span>) { 307 cluster.<span class="hljs-title function_">fork</span>(); <span class="hljs-comment">// Works ok.</span> 308 cluster.<span class="hljs-title function_">fork</span>(); <span class="hljs-comment">// Fails with EADDRINUSE.</span> 309} <span class="hljs-keyword">else</span> { 310 <span class="hljs-keyword">const</span> s = dgram.<span class="hljs-title function_">createSocket</span>(<span class="hljs-string">'udp4'</span>); 311 s.<span class="hljs-title function_">bind</span>(<span class="hljs-number">1234</span>, <span class="hljs-function">() =></span> { 312 s.<span class="hljs-title function_">addMembership</span>(<span class="hljs-string">'224.0.0.114'</span>); 313 }); 314}</code></pre> 315<h4><code>socket.addSourceSpecificMembership(sourceAddress, groupAddress[, multicastInterface])</code><span><a class="mark" href="#dgram_socket_addsourcespecificmembership_sourceaddress_groupaddress_multicastinterface" id="dgram_socket_addsourcespecificmembership_sourceaddress_groupaddress_multicastinterface">#</a></span></h4> 316<div class="api_metadata"> 317<span>Added in: v13.1.0, v12.16.0</span> 318</div> 319<ul> 320<li><code>sourceAddress</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 321<li><code>groupAddress</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 322<li><code>multicastInterface</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 323</ul> 324<p>Tells the kernel to join a source-specific multicast channel at the given 325<code>sourceAddress</code> and <code>groupAddress</code>, using the <code>multicastInterface</code> with the 326<code>IP_ADD_SOURCE_MEMBERSHIP</code> socket option. If the <code>multicastInterface</code> argument 327is not specified, the operating system will choose one interface and will add 328membership to it. To add membership to every available interface, call 329<code>socket.addSourceSpecificMembership()</code> multiple times, once per interface.</p> 330<p>When called on an unbound socket, this method will implicitly bind to a random 331port, listening on all interfaces.</p> 332<h4><code>socket.address()</code><span><a class="mark" href="#dgram_socket_address" id="dgram_socket_address">#</a></span></h4> 333<div class="api_metadata"> 334<span>Added in: v0.1.99</span> 335</div> 336<ul> 337<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 338</ul> 339<p>Returns an object containing the address information for a socket. 340For UDP sockets, this object will contain <code>address</code>, <code>family</code> and <code>port</code> 341properties.</p> 342<p>This method throws <code>EBADF</code> if called on an unbound socket.</p> 343<h4><code>socket.bind([port][, address][, callback])</code><span><a class="mark" href="#dgram_socket_bind_port_address_callback" id="dgram_socket_bind_port_address_callback">#</a></span></h4> 344<div class="api_metadata"> 345<details class="changelog"><summary>History</summary> 346<table> 347<tbody><tr><th>Version</th><th>Changes</th></tr> 348<tr><td>v0.9.1</td> 349<td><p>The method was changed to an asynchronous execution model. Legacy code would need to be changed to pass a callback function to the method call.</p></td></tr> 350<tr><td>v0.1.99</td> 351<td><p><span>Added in: v0.1.99</span></p></td></tr> 352</tbody></table> 353</details> 354</div> 355<ul> 356<li><code>port</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 357<li><code>address</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 358<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> with no parameters. Called when binding is complete.</li> 359</ul> 360<p>For UDP sockets, causes the <code>dgram.Socket</code> to listen for datagram 361messages on a named <code>port</code> and optional <code>address</code>. If <code>port</code> is not 362specified or is <code>0</code>, the operating system will attempt to bind to a 363random port. If <code>address</code> is not specified, the operating system will 364attempt to listen on all addresses. Once binding is complete, a 365<code>'listening'</code> event is emitted and the optional <code>callback</code> function is 366called.</p> 367<p>Specifying both a <code>'listening'</code> event listener and passing a 368<code>callback</code> to the <code>socket.bind()</code> method is not harmful but not very 369useful.</p> 370<p>A bound datagram socket keeps the Node.js process running to receive 371datagram messages.</p> 372<p>If binding fails, an <code>'error'</code> event is generated. In rare case (e.g. 373attempting to bind with a closed socket), an <a href="errors.html#errors_class_error"><code>Error</code></a> may be thrown.</p> 374<p>Example of a UDP server listening on port 41234:</p> 375<pre><code class="language-js"><span class="hljs-keyword">const</span> dgram = <span class="hljs-built_in">require</span>(<span class="hljs-string">'dgram'</span>); 376<span class="hljs-keyword">const</span> server = dgram.<span class="hljs-title function_">createSocket</span>(<span class="hljs-string">'udp4'</span>); 377 378server.<span class="hljs-title function_">on</span>(<span class="hljs-string">'error'</span>, <span class="hljs-function">(<span class="hljs-params">err</span>) =></span> { 379 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`server error:\n<span class="hljs-subst">${err.stack}</span>`</span>); 380 server.<span class="hljs-title function_">close</span>(); 381}); 382 383server.<span class="hljs-title function_">on</span>(<span class="hljs-string">'message'</span>, <span class="hljs-function">(<span class="hljs-params">msg, rinfo</span>) =></span> { 384 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`server got: <span class="hljs-subst">${msg}</span> from <span class="hljs-subst">${rinfo.address}</span>:<span class="hljs-subst">${rinfo.port}</span>`</span>); 385}); 386 387server.<span class="hljs-title function_">on</span>(<span class="hljs-string">'listening'</span>, <span class="hljs-function">() =></span> { 388 <span class="hljs-keyword">const</span> address = server.<span class="hljs-title function_">address</span>(); 389 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`server listening <span class="hljs-subst">${address.address}</span>:<span class="hljs-subst">${address.port}</span>`</span>); 390}); 391 392server.<span class="hljs-title function_">bind</span>(<span class="hljs-number">41234</span>); 393<span class="hljs-comment">// Prints: server listening 0.0.0.0:41234</span></code></pre> 394<h4><code>socket.bind(options[, callback])</code><span><a class="mark" href="#dgram_socket_bind_options_callback" id="dgram_socket_bind_options_callback">#</a></span></h4> 395<div class="api_metadata"> 396<span>Added in: v0.11.14</span> 397</div> 398<ul> 399<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Required. Supports the following properties: 400<ul> 401<li><code>port</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 402<li><code>address</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 403<li><code>exclusive</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 404<li><code>fd</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 405</ul> 406</li> 407<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li> 408</ul> 409<p>For UDP sockets, causes the <code>dgram.Socket</code> to listen for datagram 410messages on a named <code>port</code> and optional <code>address</code> that are passed as 411properties of an <code>options</code> object passed as the first argument. If 412<code>port</code> is not specified or is <code>0</code>, the operating system will attempt 413to bind to a random port. If <code>address</code> is not specified, the operating 414system will attempt to listen on all addresses. Once binding is 415complete, a <code>'listening'</code> event is emitted and the optional <code>callback</code> 416function is called.</p> 417<p>The <code>options</code> object may contain a <code>fd</code> property. When a <code>fd</code> greater 418than <code>0</code> is set, it will wrap around an existing socket with the given 419file descriptor. In this case, the properties of <code>port</code> and <code>address</code> 420will be ignored.</p> 421<p>Specifying both a <code>'listening'</code> event listener and passing a 422<code>callback</code> to the <code>socket.bind()</code> method is not harmful but not very 423useful.</p> 424<p>The <code>options</code> object may contain an additional <code>exclusive</code> property that is 425used when using <code>dgram.Socket</code> objects with the <a href="cluster.html"><code>cluster</code></a> module. When 426<code>exclusive</code> is set to <code>false</code> (the default), cluster workers will use the same 427underlying socket handle allowing connection handling duties to be shared. 428When <code>exclusive</code> is <code>true</code>, however, the handle is not shared and attempted 429port sharing results in an error.</p> 430<p>A bound datagram socket keeps the Node.js process running to receive 431datagram messages.</p> 432<p>If binding fails, an <code>'error'</code> event is generated. In rare case (e.g. 433attempting to bind with a closed socket), an <a href="errors.html#errors_class_error"><code>Error</code></a> may be thrown.</p> 434<p>An example socket listening on an exclusive port is shown below.</p> 435<pre><code class="language-js">socket.<span class="hljs-title function_">bind</span>({ 436 <span class="hljs-attr">address</span>: <span class="hljs-string">'localhost'</span>, 437 <span class="hljs-attr">port</span>: <span class="hljs-number">8000</span>, 438 <span class="hljs-attr">exclusive</span>: <span class="hljs-literal">true</span> 439});</code></pre> 440<h4><code>socket.close([callback])</code><span><a class="mark" href="#dgram_socket_close_callback" id="dgram_socket_close_callback">#</a></span></h4> 441<div class="api_metadata"> 442<span>Added in: v0.1.99</span> 443</div> 444<ul> 445<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Called when the socket has been closed.</li> 446</ul> 447<p>Close the underlying socket and stop listening for data on it. If a callback is 448provided, it is added as a listener for the <a href="#dgram_event_close"><code>'close'</code></a> event.</p> 449<h4><code>socket.connect(port[, address][, callback])</code><span><a class="mark" href="#dgram_socket_connect_port_address_callback" id="dgram_socket_connect_port_address_callback">#</a></span></h4> 450<div class="api_metadata"> 451<span>Added in: v12.0.0</span> 452</div> 453<ul> 454<li><code>port</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 455<li><code>address</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 456<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Called when the connection is completed or on error.</li> 457</ul> 458<p>Associates the <code>dgram.Socket</code> to a remote address and port. Every 459message sent by this handle is automatically sent to that destination. Also, 460the socket will only receive messages from that remote peer. 461Trying to call <code>connect()</code> on an already connected socket will result 462in an <a href="errors.html#errors_err_socket_dgram_is_connected"><code>ERR_SOCKET_DGRAM_IS_CONNECTED</code></a> exception. If <code>address</code> is not 463provided, <code>'127.0.0.1'</code> (for <code>udp4</code> sockets) or <code>'::1'</code> (for <code>udp6</code> sockets) 464will be used by default. Once the connection is complete, a <code>'connect'</code> event 465is emitted and the optional <code>callback</code> function is called. In case of failure, 466the <code>callback</code> is called or, failing this, an <code>'error'</code> event is emitted.</p> 467<h4><code>socket.disconnect()</code><span><a class="mark" href="#dgram_socket_disconnect" id="dgram_socket_disconnect">#</a></span></h4> 468<div class="api_metadata"> 469<span>Added in: v12.0.0</span> 470</div> 471<p>A synchronous function that disassociates a connected <code>dgram.Socket</code> from 472its remote address. Trying to call <code>disconnect()</code> on an unbound or already 473disconnected socket will result in an <a href="errors.html#errors_err_socket_dgram_not_connected"><code>ERR_SOCKET_DGRAM_NOT_CONNECTED</code></a> 474exception.</p> 475<h4><code>socket.dropMembership(multicastAddress[, multicastInterface])</code><span><a class="mark" href="#dgram_socket_dropmembership_multicastaddress_multicastinterface" id="dgram_socket_dropmembership_multicastaddress_multicastinterface">#</a></span></h4> 476<div class="api_metadata"> 477<span>Added in: v0.6.9</span> 478</div> 479<ul> 480<li><code>multicastAddress</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 481<li><code>multicastInterface</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 482</ul> 483<p>Instructs the kernel to leave a multicast group at <code>multicastAddress</code> using the 484<code>IP_DROP_MEMBERSHIP</code> socket option. This method is automatically called by the 485kernel when the socket is closed or the process terminates, so most apps will 486never have reason to call this.</p> 487<p>If <code>multicastInterface</code> is not specified, the operating system will attempt to 488drop membership on all valid interfaces.</p> 489<h4><code>socket.dropSourceSpecificMembership(sourceAddress, groupAddress[, multicastInterface])</code><span><a class="mark" href="#dgram_socket_dropsourcespecificmembership_sourceaddress_groupaddress_multicastinterface" id="dgram_socket_dropsourcespecificmembership_sourceaddress_groupaddress_multicastinterface">#</a></span></h4> 490<div class="api_metadata"> 491<span>Added in: v13.1.0, v12.16.0</span> 492</div> 493<ul> 494<li><code>sourceAddress</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 495<li><code>groupAddress</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 496<li><code>multicastInterface</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 497</ul> 498<p>Instructs the kernel to leave a source-specific multicast channel at the given 499<code>sourceAddress</code> and <code>groupAddress</code> using the <code>IP_DROP_SOURCE_MEMBERSHIP</code> 500socket option. This method is automatically called by the kernel when the 501socket is closed or the process terminates, so most apps will never have 502reason to call this.</p> 503<p>If <code>multicastInterface</code> is not specified, the operating system will attempt to 504drop membership on all valid interfaces.</p> 505<h4><code>socket.getRecvBufferSize()</code><span><a class="mark" href="#dgram_socket_getrecvbuffersize" id="dgram_socket_getrecvbuffersize">#</a></span></h4> 506<div class="api_metadata"> 507<span>Added in: v8.7.0</span> 508</div> 509<ul> 510<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> the <code>SO_RCVBUF</code> socket receive buffer size in bytes.</li> 511</ul> 512<p>This method throws <a href="errors.html#errors_err_socket_buffer_size"><code>ERR_SOCKET_BUFFER_SIZE</code></a> if called on an unbound socket.</p> 513<h4><code>socket.getSendBufferSize()</code><span><a class="mark" href="#dgram_socket_getsendbuffersize" id="dgram_socket_getsendbuffersize">#</a></span></h4> 514<div class="api_metadata"> 515<span>Added in: v8.7.0</span> 516</div> 517<ul> 518<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> the <code>SO_SNDBUF</code> socket send buffer size in bytes.</li> 519</ul> 520<p>This method throws <a href="errors.html#errors_err_socket_buffer_size"><code>ERR_SOCKET_BUFFER_SIZE</code></a> if called on an unbound socket.</p> 521<h4><code>socket.ref()</code><span><a class="mark" href="#dgram_socket_ref" id="dgram_socket_ref">#</a></span></h4> 522<div class="api_metadata"> 523<span>Added in: v0.9.1</span> 524</div> 525<ul> 526<li>Returns: <a href="dgram.html#dgram_class_dgram_socket" class="type"><dgram.Socket></a></li> 527</ul> 528<p>By default, binding a socket will cause it to block the Node.js process from 529exiting as long as the socket is open. The <code>socket.unref()</code> method can be used 530to exclude the socket from the reference counting that keeps the Node.js 531process active. The <code>socket.ref()</code> method adds the socket back to the reference 532counting and restores the default behavior.</p> 533<p>Calling <code>socket.ref()</code> multiples times will have no additional effect.</p> 534<p>The <code>socket.ref()</code> method returns a reference to the socket so calls can be 535chained.</p> 536<h4><code>socket.remoteAddress()</code><span><a class="mark" href="#dgram_socket_remoteaddress" id="dgram_socket_remoteaddress">#</a></span></h4> 537<div class="api_metadata"> 538<span>Added in: v12.0.0</span> 539</div> 540<ul> 541<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 542</ul> 543<p>Returns an object containing the <code>address</code>, <code>family</code>, and <code>port</code> of the remote 544endpoint. This method throws an <a href="errors.html#errors_err_socket_dgram_not_connected"><code>ERR_SOCKET_DGRAM_NOT_CONNECTED</code></a> exception 545if the socket is not connected.</p> 546<h4><code>socket.send(msg[, offset, length][, port][, address][, callback])</code><span><a class="mark" href="#dgram_socket_send_msg_offset_length_port_address_callback" id="dgram_socket_send_msg_offset_length_port_address_callback">#</a></span></h4> 547<div class="api_metadata"> 548<details class="changelog"><summary>History</summary> 549<table> 550<tbody><tr><th>Version</th><th>Changes</th></tr> 551<tr><td>v14.5.0</td> 552<td><p>The <code>msg</code> parameter can now be any <code>TypedArray</code> or <code>DataView</code>.</p></td></tr> 553<tr><td>v12.0.0</td> 554<td><p>Added support for sending data on connected sockets.</p></td></tr> 555<tr><td>v8.0.0</td> 556<td><p>The <code>msg</code> parameter can be an <code>Uint8Array</code> now.</p></td></tr> 557<tr><td>v8.0.0</td> 558<td><p>The <code>address</code> parameter is always optional now.</p></td></tr> 559<tr><td>v6.0.0</td> 560<td><p>On success, <code>callback</code> will now be called with an <code>error</code> argument of <code>null</code> rather than <code>0</code>.</p></td></tr> 561<tr><td>v5.7.0</td> 562<td><p>The <code>msg</code> parameter can be an array now. Also, the <code>offset</code> and <code>length</code> parameters are optional now.</p></td></tr> 563<tr><td>v0.1.99</td> 564<td><p><span>Added in: v0.1.99</span></p></td></tr> 565</tbody></table> 566</details> 567</div> 568<ul> 569<li><code>msg</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a> | <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/Array" class="type"><Array></a> Message to be sent.</li> 570<li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Offset in the buffer where the message starts.</li> 571<li><code>length</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes in the message.</li> 572<li><code>port</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Destination port.</li> 573<li><code>address</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Destination host name or IP address.</li> 574<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Called when the message has been sent.</li> 575</ul> 576<p>Broadcasts a datagram on the socket. 577For connectionless sockets, the destination <code>port</code> and <code>address</code> must be 578specified. Connected sockets, on the other hand, will use their associated 579remote endpoint, so the <code>port</code> and <code>address</code> arguments must not be set.</p> 580<p>The <code>msg</code> argument contains the message to be sent. 581Depending on its type, different behavior can apply. If <code>msg</code> is a <code>Buffer</code>, 582any <code>TypedArray</code> or a <code>DataView</code>, 583the <code>offset</code> and <code>length</code> specify the offset within the <code>Buffer</code> where the 584message begins and the number of bytes in the message, respectively. 585If <code>msg</code> is a <code>String</code>, then it is automatically converted to a <code>Buffer</code> 586with <code>'utf8'</code> encoding. With messages that 587contain multi-byte characters, <code>offset</code> and <code>length</code> will be calculated with 588respect to <a href="buffer.html#buffer_static_method_buffer_bytelength_string_encoding">byte length</a> and not the character position. 589If <code>msg</code> is an array, <code>offset</code> and <code>length</code> must not be specified.</p> 590<p>The <code>address</code> argument is a string. If the value of <code>address</code> is a host name, 591DNS will be used to resolve the address of the host. If <code>address</code> is not 592provided or otherwise falsy, <code>'127.0.0.1'</code> (for <code>udp4</code> sockets) or <code>'::1'</code> 593(for <code>udp6</code> sockets) will be used by default.</p> 594<p>If the socket has not been previously bound with a call to <code>bind</code>, the socket 595is assigned a random port number and is bound to the "all interfaces" address 596(<code>'0.0.0.0'</code> for <code>udp4</code> sockets, <code>'::0'</code> for <code>udp6</code> sockets.)</p> 597<p>An optional <code>callback</code> function may be specified to as a way of reporting 598DNS errors or for determining when it is safe to reuse the <code>buf</code> object. 599DNS lookups delay the time to send for at least one tick of the 600Node.js event loop.</p> 601<p>The only way to know for sure that the datagram has been sent is by using a 602<code>callback</code>. If an error occurs and a <code>callback</code> is given, the error will be 603passed as the first argument to the <code>callback</code>. If a <code>callback</code> is not given, 604the error is emitted as an <code>'error'</code> event on the <code>socket</code> object.</p> 605<p>Offset and length are optional but both <em>must</em> be set if either are used. 606They are supported only when the first argument is a <code>Buffer</code>, a <code>TypedArray</code>, 607or a <code>DataView</code>.</p> 608<p>This method throws <a href="errors.html#errors_err_socket_bad_port"><code>ERR_SOCKET_BAD_PORT</code></a> if called on an unbound socket.</p> 609<p>Example of sending a UDP packet to a port on <code>localhost</code>;</p> 610<pre><code class="language-js"><span class="hljs-keyword">const</span> dgram = <span class="hljs-built_in">require</span>(<span class="hljs-string">'dgram'</span>); 611<span class="hljs-keyword">const</span> message = <span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">from</span>(<span class="hljs-string">'Some bytes'</span>); 612<span class="hljs-keyword">const</span> client = dgram.<span class="hljs-title function_">createSocket</span>(<span class="hljs-string">'udp4'</span>); 613client.<span class="hljs-title function_">send</span>(message, <span class="hljs-number">41234</span>, <span class="hljs-string">'localhost'</span>, <span class="hljs-function">(<span class="hljs-params">err</span>) =></span> { 614 client.<span class="hljs-title function_">close</span>(); 615});</code></pre> 616<p>Example of sending a UDP packet composed of multiple buffers to a port on 617<code>127.0.0.1</code>;</p> 618<pre><code class="language-js"><span class="hljs-keyword">const</span> dgram = <span class="hljs-built_in">require</span>(<span class="hljs-string">'dgram'</span>); 619<span class="hljs-keyword">const</span> buf1 = <span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">from</span>(<span class="hljs-string">'Some '</span>); 620<span class="hljs-keyword">const</span> buf2 = <span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">from</span>(<span class="hljs-string">'bytes'</span>); 621<span class="hljs-keyword">const</span> client = dgram.<span class="hljs-title function_">createSocket</span>(<span class="hljs-string">'udp4'</span>); 622client.<span class="hljs-title function_">send</span>([buf1, buf2], <span class="hljs-number">41234</span>, <span class="hljs-function">(<span class="hljs-params">err</span>) =></span> { 623 client.<span class="hljs-title function_">close</span>(); 624});</code></pre> 625<p>Sending multiple buffers might be faster or slower depending on the 626application and operating system. Run benchmarks to 627determine the optimal strategy on a case-by-case basis. Generally speaking, 628however, sending multiple buffers is faster.</p> 629<p>Example of sending a UDP packet using a socket connected to a port on 630<code>localhost</code>:</p> 631<pre><code class="language-js"><span class="hljs-keyword">const</span> dgram = <span class="hljs-built_in">require</span>(<span class="hljs-string">'dgram'</span>); 632<span class="hljs-keyword">const</span> message = <span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">from</span>(<span class="hljs-string">'Some bytes'</span>); 633<span class="hljs-keyword">const</span> client = dgram.<span class="hljs-title function_">createSocket</span>(<span class="hljs-string">'udp4'</span>); 634client.<span class="hljs-title function_">connect</span>(<span class="hljs-number">41234</span>, <span class="hljs-string">'localhost'</span>, <span class="hljs-function">(<span class="hljs-params">err</span>) =></span> { 635 client.<span class="hljs-title function_">send</span>(message, <span class="hljs-function">(<span class="hljs-params">err</span>) =></span> { 636 client.<span class="hljs-title function_">close</span>(); 637 }); 638});</code></pre> 639<h5>Note about UDP datagram size<span><a class="mark" href="#dgram_note_about_udp_datagram_size" id="dgram_note_about_udp_datagram_size">#</a></span></h5> 640<p>The maximum size of an IPv4/v6 datagram depends on the <code>MTU</code> 641(Maximum Transmission Unit) and on the <code>Payload Length</code> field size.</p> 642<ul> 643<li> 644<p>The <code>Payload Length</code> field is 16 bits wide, which means that a normal 645payload cannot exceed 64K octets including the internet header and data 646(65,507 bytes = 65,535 − 8 bytes UDP header − 20 bytes IP header); 647this is generally true for loopback interfaces, but such long datagram 648messages are impractical for most hosts and networks.</p> 649</li> 650<li> 651<p>The <code>MTU</code> is the largest size a given link layer technology can support for 652datagram messages. For any link, IPv4 mandates a minimum <code>MTU</code> of 68 653octets, while the recommended <code>MTU</code> for IPv4 is 576 (typically recommended 654as the <code>MTU</code> for dial-up type applications), whether they arrive whole or in 655fragments.</p> 656<p>For IPv6, the minimum <code>MTU</code> is 1280 octets. However, the mandatory minimum 657fragment reassembly buffer size is 1500 octets. The value of 68 octets is 658very small, since most current link layer technologies, like Ethernet, have a 659minimum <code>MTU</code> of 1500.</p> 660</li> 661</ul> 662<p>It is impossible to know in advance the MTU of each link through which 663a packet might travel. Sending a datagram greater than the receiver <code>MTU</code> will 664not work because the packet will get silently dropped without informing the 665source that the data did not reach its intended recipient.</p> 666<h4><code>socket.setBroadcast(flag)</code><span><a class="mark" href="#dgram_socket_setbroadcast_flag" id="dgram_socket_setbroadcast_flag">#</a></span></h4> 667<div class="api_metadata"> 668<span>Added in: v0.6.9</span> 669</div> 670<ul> 671<li><code>flag</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 672</ul> 673<p>Sets or clears the <code>SO_BROADCAST</code> socket option. When set to <code>true</code>, UDP 674packets may be sent to a local interface's broadcast address.</p> 675<p>This method throws <code>EBADF</code> if called on an unbound socket.</p> 676<h4><code>socket.setMulticastInterface(multicastInterface)</code><span><a class="mark" href="#dgram_socket_setmulticastinterface_multicastinterface" id="dgram_socket_setmulticastinterface_multicastinterface">#</a></span></h4> 677<div class="api_metadata"> 678<span>Added in: v8.6.0</span> 679</div> 680<ul> 681<li><code>multicastInterface</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 682</ul> 683<p><em>All references to scope in this section are referring to 684<a href="https://en.wikipedia.org/wiki/IPv6_address#Scoped_literal_IPv6_addresses">IPv6 Zone Indices</a>, which are defined by <a href="https://tools.ietf.org/html/rfc4007">RFC 4007</a>. In string form, an IP 685with a scope index is written as <code>'IP%scope'</code> where scope is an interface name 686or interface number.</em></p> 687<p>Sets the default outgoing multicast interface of the socket to a chosen 688interface or back to system interface selection. The <code>multicastInterface</code> must 689be a valid string representation of an IP from the socket's family.</p> 690<p>For IPv4 sockets, this should be the IP configured for the desired physical 691interface. All packets sent to multicast on the socket will be sent on the 692interface determined by the most recent successful use of this call.</p> 693<p>For IPv6 sockets, <code>multicastInterface</code> should include a scope to indicate the 694interface as in the examples that follow. In IPv6, individual <code>send</code> calls can 695also use explicit scope in addresses, so only packets sent to a multicast 696address without specifying an explicit scope are affected by the most recent 697successful use of this call.</p> 698<p>This method throws <code>EBADF</code> if called on an unbound socket.</p> 699<h5>Example: IPv6 outgoing multicast interface<span><a class="mark" href="#dgram_example_ipv6_outgoing_multicast_interface" id="dgram_example_ipv6_outgoing_multicast_interface">#</a></span></h5> 700<p>On most systems, where scope format uses the interface name:</p> 701<pre><code class="language-js"><span class="hljs-keyword">const</span> socket = dgram.<span class="hljs-title function_">createSocket</span>(<span class="hljs-string">'udp6'</span>); 702 703socket.<span class="hljs-title function_">bind</span>(<span class="hljs-number">1234</span>, <span class="hljs-function">() =></span> { 704 socket.<span class="hljs-title function_">setMulticastInterface</span>(<span class="hljs-string">'::%eth1'</span>); 705});</code></pre> 706<p>On Windows, where scope format uses an interface number:</p> 707<pre><code class="language-js"><span class="hljs-keyword">const</span> socket = dgram.<span class="hljs-title function_">createSocket</span>(<span class="hljs-string">'udp6'</span>); 708 709socket.<span class="hljs-title function_">bind</span>(<span class="hljs-number">1234</span>, <span class="hljs-function">() =></span> { 710 socket.<span class="hljs-title function_">setMulticastInterface</span>(<span class="hljs-string">'::%2'</span>); 711});</code></pre> 712<h5>Example: IPv4 outgoing multicast interface<span><a class="mark" href="#dgram_example_ipv4_outgoing_multicast_interface" id="dgram_example_ipv4_outgoing_multicast_interface">#</a></span></h5> 713<p>All systems use an IP of the host on the desired physical interface:</p> 714<pre><code class="language-js"><span class="hljs-keyword">const</span> socket = dgram.<span class="hljs-title function_">createSocket</span>(<span class="hljs-string">'udp4'</span>); 715 716socket.<span class="hljs-title function_">bind</span>(<span class="hljs-number">1234</span>, <span class="hljs-function">() =></span> { 717 socket.<span class="hljs-title function_">setMulticastInterface</span>(<span class="hljs-string">'10.0.0.2'</span>); 718});</code></pre> 719<h5>Call results<span><a class="mark" href="#dgram_call_results" id="dgram_call_results">#</a></span></h5> 720<p>A call on a socket that is not ready to send or no longer open may throw a <em>Not 721running</em> <a href="errors.html#errors_class_error"><code>Error</code></a>.</p> 722<p>If <code>multicastInterface</code> can not be parsed into an IP then an <em>EINVAL</em> 723<a href="errors.html#errors_class_systemerror"><code>System Error</code></a> is thrown.</p> 724<p>On IPv4, if <code>multicastInterface</code> is a valid address but does not match any 725interface, or if the address does not match the family then 726a <a href="errors.html#errors_class_systemerror"><code>System Error</code></a> such as <code>EADDRNOTAVAIL</code> or <code>EPROTONOSUP</code> is thrown.</p> 727<p>On IPv6, most errors with specifying or omitting scope will result in the socket 728continuing to use (or returning to) the system's default interface selection.</p> 729<p>A socket's address family's ANY address (IPv4 <code>'0.0.0.0'</code> or IPv6 <code>'::'</code>) can be 730used to return control of the sockets default outgoing interface to the system 731for future multicast packets.</p> 732<h4><code>socket.setMulticastLoopback(flag)</code><span><a class="mark" href="#dgram_socket_setmulticastloopback_flag" id="dgram_socket_setmulticastloopback_flag">#</a></span></h4> 733<div class="api_metadata"> 734<span>Added in: v0.3.8</span> 735</div> 736<ul> 737<li><code>flag</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 738</ul> 739<p>Sets or clears the <code>IP_MULTICAST_LOOP</code> socket option. When set to <code>true</code>, 740multicast packets will also be received on the local interface.</p> 741<p>This method throws <code>EBADF</code> if called on an unbound socket.</p> 742<h4><code>socket.setMulticastTTL(ttl)</code><span><a class="mark" href="#dgram_socket_setmulticastttl_ttl" id="dgram_socket_setmulticastttl_ttl">#</a></span></h4> 743<div class="api_metadata"> 744<span>Added in: v0.3.8</span> 745</div> 746<ul> 747<li><code>ttl</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 748</ul> 749<p>Sets the <code>IP_MULTICAST_TTL</code> socket option. While TTL generally stands for 750"Time to Live", in this context it specifies the number of IP hops that a 751packet is allowed to travel through, specifically for multicast traffic. Each 752router or gateway that forwards a packet decrements the TTL. If the TTL is 753decremented to 0 by a router, it will not be forwarded.</p> 754<p>The <code>ttl</code> argument may be between 0 and 255. The default on most systems is <code>1</code>.</p> 755<p>This method throws <code>EBADF</code> if called on an unbound socket.</p> 756<h4><code>socket.setRecvBufferSize(size)</code><span><a class="mark" href="#dgram_socket_setrecvbuffersize_size" id="dgram_socket_setrecvbuffersize_size">#</a></span></h4> 757<div class="api_metadata"> 758<span>Added in: v8.7.0</span> 759</div> 760<ul> 761<li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 762</ul> 763<p>Sets the <code>SO_RCVBUF</code> socket option. Sets the maximum socket receive buffer 764in bytes.</p> 765<p>This method throws <a href="errors.html#errors_err_socket_buffer_size"><code>ERR_SOCKET_BUFFER_SIZE</code></a> if called on an unbound socket.</p> 766<h4><code>socket.setSendBufferSize(size)</code><span><a class="mark" href="#dgram_socket_setsendbuffersize_size" id="dgram_socket_setsendbuffersize_size">#</a></span></h4> 767<div class="api_metadata"> 768<span>Added in: v8.7.0</span> 769</div> 770<ul> 771<li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 772</ul> 773<p>Sets the <code>SO_SNDBUF</code> socket option. Sets the maximum socket send buffer 774in bytes.</p> 775<p>This method throws <a href="errors.html#errors_err_socket_buffer_size"><code>ERR_SOCKET_BUFFER_SIZE</code></a> if called on an unbound socket.</p> 776<h4><code>socket.setTTL(ttl)</code><span><a class="mark" href="#dgram_socket_setttl_ttl" id="dgram_socket_setttl_ttl">#</a></span></h4> 777<div class="api_metadata"> 778<span>Added in: v0.1.101</span> 779</div> 780<ul> 781<li><code>ttl</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 782</ul> 783<p>Sets the <code>IP_TTL</code> socket option. While TTL generally stands for "Time to Live", 784in this context it specifies the number of IP hops that a packet is allowed to 785travel through. Each router or gateway that forwards a packet decrements the 786TTL. If the TTL is decremented to 0 by a router, it will not be forwarded. 787Changing TTL values is typically done for network probes or when multicasting.</p> 788<p>The <code>ttl</code> argument may be between between 1 and 255. The default on most systems 789is 64.</p> 790<p>This method throws <code>EBADF</code> if called on an unbound socket.</p> 791<h4><code>socket.unref()</code><span><a class="mark" href="#dgram_socket_unref" id="dgram_socket_unref">#</a></span></h4> 792<div class="api_metadata"> 793<span>Added in: v0.9.1</span> 794</div> 795<ul> 796<li>Returns: <a href="dgram.html#dgram_class_dgram_socket" class="type"><dgram.Socket></a></li> 797</ul> 798<p>By default, binding a socket will cause it to block the Node.js process from 799exiting as long as the socket is open. The <code>socket.unref()</code> method can be used 800to exclude the socket from the reference counting that keeps the Node.js 801process active, allowing the process to exit even if the socket is still 802listening.</p> 803<p>Calling <code>socket.unref()</code> multiple times will have no addition effect.</p> 804<p>The <code>socket.unref()</code> method returns a reference to the socket so calls can be 805chained.</p> 806</section><section><h3><code>dgram</code> module functions<span><a class="mark" href="#dgram_dgram_module_functions" id="dgram_dgram_module_functions">#</a></span></h3> 807<h4><code>dgram.createSocket(options[, callback])</code><span><a class="mark" href="#dgram_dgram_createsocket_options_callback" id="dgram_dgram_createsocket_options_callback">#</a></span></h4> 808<div class="api_metadata"> 809<details class="changelog"><summary>History</summary> 810<table> 811<tbody><tr><th>Version</th><th>Changes</th></tr> 812<tr><td>v14.17.0</td> 813<td><p>AbortSignal support was added.</p></td></tr> 814<tr><td>v11.4.0</td> 815<td><p>The <code>ipv6Only</code> option is supported.</p></td></tr> 816<tr><td>v8.7.0</td> 817<td><p>The <code>recvBufferSize</code> and <code>sendBufferSize</code> options are supported now.</p></td></tr> 818<tr><td>v8.6.0</td> 819<td><p>The <code>lookup</code> option is supported.</p></td></tr> 820<tr><td>v0.11.13</td> 821<td><p><span>Added in: v0.11.13</span></p></td></tr> 822</tbody></table> 823</details> 824</div> 825<ul> 826<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Available options are: 827<ul> 828<li><code>type</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The family of socket. Must be either <code>'udp4'</code> or <code>'udp6'</code>. 829Required.</li> 830<li><code>reuseAddr</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code> <a href="#dgram_socket_bind_port_address_callback"><code>socket.bind()</code></a> will reuse the 831address, even if another process has already bound a socket on it. 832<strong>Default:</strong> <code>false</code>.</li> 833<li><code>ipv6Only</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Setting <code>ipv6Only</code> to <code>true</code> will 834disable dual-stack support, i.e., binding to address <code>::</code> won't make 835<code>0.0.0.0</code> be bound. <strong>Default:</strong> <code>false</code>.</li> 836<li><code>recvBufferSize</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Sets the <code>SO_RCVBUF</code> socket value.</li> 837<li><code>sendBufferSize</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Sets the <code>SO_SNDBUF</code> socket value.</li> 838<li><code>lookup</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Custom lookup function. <strong>Default:</strong> <a href="dns.html#dns_dns_lookup_hostname_options_callback"><code>dns.lookup()</code></a>.</li> 839<li><code>signal</code> <a href="globals.html#globals_class_abortsignal" class="type"><AbortSignal></a> An AbortSignal that may be used to close a socket.</li> 840</ul> 841</li> 842<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Attached as a listener for <code>'message'</code> events. Optional.</li> 843<li>Returns: <a href="dgram.html#dgram_class_dgram_socket" class="type"><dgram.Socket></a></li> 844</ul> 845<p>Creates a <code>dgram.Socket</code> object. Once the socket is created, calling 846<a href="#dgram_socket_bind_port_address_callback"><code>socket.bind()</code></a> will instruct the socket to begin listening for datagram 847messages. When <code>address</code> and <code>port</code> are not passed to <a href="#dgram_socket_bind_port_address_callback"><code>socket.bind()</code></a> the 848method will bind the socket to the "all interfaces" address on a random port 849(it does the right thing for both <code>udp4</code> and <code>udp6</code> sockets). The bound address 850and port can be retrieved using <a href="#dgram_socket_address"><code>socket.address().address</code></a> and 851<a href="#dgram_socket_address"><code>socket.address().port</code></a>.</p> 852<p>If the <code>signal</code> option is enabled, calling <code>.abort()</code> on the corresponding 853<code>AbortController</code> is similar to calling <code>.close()</code> on the socket:</p> 854<pre><code class="language-js"><span class="hljs-keyword">const</span> controller = <span class="hljs-keyword">new</span> <span class="hljs-title class_">AbortController</span>(); 855<span class="hljs-keyword">const</span> { signal } = controller; 856<span class="hljs-keyword">const</span> server = dgram.<span class="hljs-title function_">createSocket</span>({ <span class="hljs-attr">type</span>: <span class="hljs-string">'udp4'</span>, signal }); 857server.<span class="hljs-title function_">on</span>(<span class="hljs-string">'message'</span>, <span class="hljs-function">(<span class="hljs-params">msg, rinfo</span>) =></span> { 858 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`server got: <span class="hljs-subst">${msg}</span> from <span class="hljs-subst">${rinfo.address}</span>:<span class="hljs-subst">${rinfo.port}</span>`</span>); 859}); 860<span class="hljs-comment">// Later, when you want to close the server.</span> 861controller.<span class="hljs-title function_">abort</span>();</code></pre> 862<h4><code>dgram.createSocket(type[, callback])</code><span><a class="mark" href="#dgram_dgram_createsocket_type_callback" id="dgram_dgram_createsocket_type_callback">#</a></span></h4> 863<div class="api_metadata"> 864<span>Added in: v0.1.99</span> 865</div> 866<ul> 867<li><code>type</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Either <code>'udp4'</code> or <code>'udp6'</code>.</li> 868<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Attached as a listener to <code>'message'</code> events.</li> 869<li>Returns: <a href="dgram.html#dgram_class_dgram_socket" class="type"><dgram.Socket></a></li> 870</ul> 871<p>Creates a <code>dgram.Socket</code> object of the specified <code>type</code>.</p> 872<p>Once the socket is created, calling <a href="#dgram_socket_bind_port_address_callback"><code>socket.bind()</code></a> will instruct the 873socket to begin listening for datagram messages. When <code>address</code> and <code>port</code> are 874not passed to <a href="#dgram_socket_bind_port_address_callback"><code>socket.bind()</code></a> the method will bind the socket to the "all 875interfaces" address on a random port (it does the right thing for both <code>udp4</code> 876and <code>udp6</code> sockets). The bound address and port can be retrieved using 877<a href="#dgram_socket_address"><code>socket.address().address</code></a> and <a href="#dgram_socket_address"><code>socket.address().port</code></a>.</p></section> 878 <!-- API END --> 879 </div> 880 </div> 881 </div> 882 <script> 883 'use strict'; 884 { 885 const kCustomPreference = 'customDarkTheme'; 886 const userSettings = sessionStorage.getItem(kCustomPreference); 887 const themeToggleButton = document.getElementById('theme-toggle-btn'); 888 if (userSettings === null && window.matchMedia) { 889 const mq = window.matchMedia('(prefers-color-scheme: dark)'); 890 if ('onchange' in mq) { 891 function mqChangeListener(e) { 892 document.body.classList.toggle('dark-mode', e.matches); 893 } 894 mq.addEventListener('change', mqChangeListener); 895 if (themeToggleButton) { 896 themeToggleButton.addEventListener('click', function() { 897 mq.removeEventListener('change', mqChangeListener); 898 }, { once: true }); 899 } 900 } 901 if (mq.matches) { 902 document.body.classList.add('dark-mode'); 903 } 904 } else if (userSettings === 'true') { 905 document.body.classList.add('dark-mode'); 906 } 907 if (themeToggleButton) { 908 themeToggleButton.hidden = false; 909 themeToggleButton.addEventListener('click', function() { 910 sessionStorage.setItem( 911 kCustomPreference, 912 document.body.classList.toggle('dark-mode') 913 ); 914 }); 915 } 916 } 917 </script> 918</body> 919</html> 920