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<code>'message'</code></a></li> 154<li><a href="#dgram_socket_addmembership_multicastaddress_multicastinterface"><code>socket.addMembership(multicastAddress[, multicastInterface])</code></a></li> 155<li><a href="#dgram_socket_addsourcespecificmembership_sourceaddress_groupaddress_multicastinterface"><code>socket.addSourceSpecificMembership(sourceAddress, groupAddress[, multicastInterface])</code></a></li> 156<li><a href="#dgram_socket_address"><code>socket.address()</code></a></li> 157<li><a href="#dgram_socket_bind_port_address_callback"><code>socket.bind([port][, address][, callback])</code></a></li> 158<li><a href="#dgram_socket_bind_options_callback"><code>socket.bind(options[, callback])</code></a></li> 159<li><a href="#dgram_socket_close_callback"><code>socket.close([callback])</code></a></li> 160<li><a href="#dgram_socket_connect_port_address_callback"><code>socket.connect(port[, address][, callback])</code></a></li> 161<li><a href="#dgram_socket_disconnect"><code>socket.disconnect()</code></a></li> 162<li><a href="#dgram_socket_dropmembership_multicastaddress_multicastinterface"><code>socket.dropMembership(multicastAddress[, multicastInterface])</code></a></li> 163<li><a href="#dgram_socket_dropsourcespecificmembership_sourceaddress_groupaddress_multicastinterface"><code>socket.dropSourceSpecificMembership(sourceAddress, groupAddress[, multicastInterface])</code></a></li> 164<li><a href="#dgram_socket_getrecvbuffersize"><code>socket.getRecvBufferSize()</code></a></li> 165<li><a href="#dgram_socket_getsendbuffersize"><code>socket.getSendBufferSize()</code></a></li> 166<li><a href="#dgram_socket_ref"><code>socket.ref()</code></a></li> 167<li><a href="#dgram_socket_remoteaddress"><code>socket.remoteAddress()</code></a></li> 168<li><a href="#dgram_socket_send_msg_offset_length_port_address_callback"><code>socket.send(msg[, offset, length][, port][, address][, callback])</code></a> 169<ul> 170<li><a href="#dgram_note_about_udp_datagram_size">Note about UDP datagram size</a></li> 171</ul> 172</li> 173<li><a href="#dgram_socket_setbroadcast_flag"><code>socket.setBroadcast(flag)</code></a></li> 174<li><a href="#dgram_socket_setmulticastinterface_multicastinterface"><code>socket.setMulticastInterface(multicastInterface)</code></a> 175<ul> 176<li><a href="#dgram_example_ipv6_outgoing_multicast_interface">Example: IPv6 outgoing multicast interface</a></li> 177<li><a href="#dgram_example_ipv4_outgoing_multicast_interface">Example: IPv4 outgoing multicast interface</a></li> 178<li><a href="#dgram_call_results">Call results</a></li> 179</ul> 180</li> 181<li><a href="#dgram_socket_setmulticastloopback_flag"><code>socket.setMulticastLoopback(flag)</code></a></li> 182<li><a href="#dgram_socket_setmulticastttl_ttl"><code>socket.setMulticastTTL(ttl)</code></a></li> 183<li><a href="#dgram_socket_setrecvbuffersize_size"><code>socket.setRecvBufferSize(size)</code></a></li> 184<li><a href="#dgram_socket_setsendbuffersize_size"><code>socket.setSendBufferSize(size)</code></a></li> 185<li><a href="#dgram_socket_setttl_ttl"><code>socket.setTTL(ttl)</code></a></li> 186<li><a href="#dgram_socket_unref"><code>socket.unref()</code></a></li> 187</ul> 188</li> 189<li><a href="#dgram_dgram_module_functions"><code>dgram</code> module functions</a> 190<ul> 191<li><a href="#dgram_dgram_createsocket_options_callback"><code>dgram.createSocket(options[, callback])</code></a></li> 192<li><a href="#dgram_dgram_createsocket_type_callback"><code>dgram.createSocket(type[, callback])</code></a></li> 193</ul> 194</li> 195</ul> 196</li> 197</ul></details> 198 199 <div id="apicontent"> 200 <h2>UDP/datagram sockets<span><a class="mark" href="#dgram_udp_datagram_sockets" id="dgram_udp_datagram_sockets">#</a></span></h2> 201 202<p></p><div class="api_stability api_stability_2"><a href="documentation.html#documentation_stability_index">Stability: 2</a> - Stable</div><p></p> 203 204<p><strong>Source Code:</strong> <a href="https://github.com/nodejs/node/blob/v14.20.1/lib/dgram.js">lib/dgram.js</a></p> 205<p>The <code>dgram</code> module provides an implementation of UDP datagram sockets.</p> 206<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>); 207<span class="hljs-keyword">const</span> server = dgram.<span class="hljs-title function_">createSocket</span>(<span class="hljs-string">'udp4'</span>); 208 209server.<span class="hljs-title function_">on</span>(<span class="hljs-string">'error'</span>, <span class="hljs-function">(<span class="hljs-params">err</span>) =></span> { 210 <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">${err.stack}</span>`</span>); 211 server.<span class="hljs-title function_">close</span>(); 212}); 213 214server.<span class="hljs-title function_">on</span>(<span class="hljs-string">'message'</span>, <span class="hljs-function">(<span class="hljs-params">msg, rinfo</span>) =></span> { 215 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`server got: <span class="hljs-subst">${msg}</span> from <span class="hljs-subst">${rinfo.address}</span>:<span class="hljs-subst">${rinfo.port}</span>`</span>); 216}); 217 218server.<span class="hljs-title function_">on</span>(<span class="hljs-string">'listening'</span>, <span class="hljs-function">() =></span> { 219 <span class="hljs-keyword">const</span> address = server.<span class="hljs-title function_">address</span>(); 220 <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>); 221}); 222 223server.<span class="hljs-title function_">bind</span>(<span class="hljs-number">41234</span>); 224<span class="hljs-comment">// Prints: server listening 0.0.0.0:41234</span></code></pre> 225<section><h3>Class: <code>dgram.Socket</code><span><a class="mark" href="#dgram_class_dgram_socket" id="dgram_class_dgram_socket">#</a></span></h3> 226<div class="api_metadata"> 227<span>Added in: v0.1.99</span> 228</div> 229<ul> 230<li>Extends: <a href="events.html#events_class_eventemitter" class="type"><EventEmitter></a></li> 231</ul> 232<p>Encapsulates the datagram functionality.</p> 233<p>New instances of <code>dgram.Socket</code> are created using <a href="#dgram_dgram_createsocket_options_callback"><code>dgram.createSocket()</code></a>. 234The <code>new</code> keyword is not to be used to create <code>dgram.Socket</code> instances.</p> 235<h4>Event: <code>'close'</code><span><a class="mark" href="#dgram_event_close" id="dgram_event_close">#</a></span></h4> 236<div class="api_metadata"> 237<span>Added in: v0.1.99</span> 238</div> 239<p>The <code>'close'</code> event is emitted after a socket is closed with <a href="#dgram_socket_close_callback"><code>close()</code></a>. 240Once triggered, no new <code>'message'</code> events will be emitted on this socket.</p> 241<h4>Event: <code>'connect'</code><span><a class="mark" href="#dgram_event_connect" id="dgram_event_connect">#</a></span></h4> 242<div class="api_metadata"> 243<span>Added in: v12.0.0</span> 244</div> 245<p>The <code>'connect'</code> event is emitted after a socket is associated to a remote 246address as a result of a successful <a href="#dgram_socket_connect_port_address_callback"><code>connect()</code></a> call.</p> 247<h4>Event: <code>'error'</code><span><a class="mark" href="#dgram_event_error" id="dgram_event_error">#</a></span></h4> 248<div class="api_metadata"> 249<span>Added in: v0.1.99</span> 250</div> 251<ul> 252<li><code>exception</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 253</ul> 254<p>The <code>'error'</code> event is emitted whenever any error occurs. The event handler 255function is passed a single <code>Error</code> object.</p> 256<h4>Event: <code>'listening'</code><span><a class="mark" href="#dgram_event_listening" id="dgram_event_listening">#</a></span></h4> 257<div class="api_metadata"> 258<span>Added in: v0.1.99</span> 259</div> 260<p>The <code>'listening'</code> event is emitted once the <code>dgram.Socket</code> is addressable and 261can receive data. This happens either explicitly with <code>socket.bind()</code> or 262implicitly the first time data is sent using <code>socket.send()</code>. 263Until the <code>dgram.Socket</code> is listening, the underlying system resources do not 264exist and calls such as <code>socket.address()</code> and <code>socket.setTTL()</code> will fail.</p> 265<h4>Event: <code>'message'</code><span><a class="mark" href="#dgram_event_message" id="dgram_event_message">#</a></span></h4> 266<div class="api_metadata"> 267<span>Added in: v0.1.99</span> 268</div> 269<p>The <code>'message'</code> event is emitted when a new datagram is available on a socket. 270The event handler function is passed two arguments: <code>msg</code> and <code>rinfo</code>.</p> 271<ul> 272<li><code>msg</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> The message.</li> 273<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. 274<ul> 275<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> 276<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> 277<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> 278<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> 279</ul> 280</li> 281</ul> 282<p>If the source address of the incoming packet is an IPv6 link-local 283address, the interface name is added to the <code>address</code>. For 284example, a packet received on the <code>en0</code> interface might have the 285address field set to <code>'fe80::2618:1234:ab11:3b9c%en0'</code>, where <code>'%en0'</code> 286is the interface name as a zone ID suffix.</p> 287<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> 288<div class="api_metadata"> 289<span>Added in: v0.6.9</span> 290</div> 291<ul> 292<li><code>multicastAddress</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 293<li><code>multicastInterface</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 294</ul> 295<p>Tells the kernel to join a multicast group at the given <code>multicastAddress</code> and 296<code>multicastInterface</code> using the <code>IP_ADD_MEMBERSHIP</code> socket option. If the 297<code>multicastInterface</code> argument is not specified, the operating system will choose 298one interface and will add membership to it. To add membership to every 299available interface, call <code>addMembership</code> multiple times, once per interface.</p> 300<p>When called on an unbound socket, this method will implicitly bind to a random 301port, listening on all interfaces.</p> 302<p>When sharing a UDP socket across multiple <code>cluster</code> workers, the 303<code>socket.addMembership()</code> function must be called only once or an 304<code>EADDRINUSE</code> error will occur:</p> 305<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>); 306<span class="hljs-keyword">const</span> dgram = <span class="hljs-built_in">require</span>(<span class="hljs-string">'dgram'</span>); 307<span class="hljs-keyword">if</span> (cluster.<span class="hljs-property">isMaster</span>) { 308 cluster.<span class="hljs-title function_">fork</span>(); <span class="hljs-comment">// Works ok.</span> 309 cluster.<span class="hljs-title function_">fork</span>(); <span class="hljs-comment">// Fails with EADDRINUSE.</span> 310} <span class="hljs-keyword">else</span> { 311 <span class="hljs-keyword">const</span> s = dgram.<span class="hljs-title function_">createSocket</span>(<span class="hljs-string">'udp4'</span>); 312 s.<span class="hljs-title function_">bind</span>(<span class="hljs-number">1234</span>, <span class="hljs-function">() =></span> { 313 s.<span class="hljs-title function_">addMembership</span>(<span class="hljs-string">'224.0.0.114'</span>); 314 }); 315}</code></pre> 316<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> 317<div class="api_metadata"> 318<span>Added in: v13.1.0, v12.16.0</span> 319</div> 320<ul> 321<li><code>sourceAddress</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 322<li><code>groupAddress</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 323<li><code>multicastInterface</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 324</ul> 325<p>Tells the kernel to join a source-specific multicast channel at the given 326<code>sourceAddress</code> and <code>groupAddress</code>, using the <code>multicastInterface</code> with the 327<code>IP_ADD_SOURCE_MEMBERSHIP</code> socket option. If the <code>multicastInterface</code> argument 328is not specified, the operating system will choose one interface and will add 329membership to it. To add membership to every available interface, call 330<code>socket.addSourceSpecificMembership()</code> multiple times, once per interface.</p> 331<p>When called on an unbound socket, this method will implicitly bind to a random 332port, listening on all interfaces.</p> 333<h4><code>socket.address()</code><span><a class="mark" href="#dgram_socket_address" id="dgram_socket_address">#</a></span></h4> 334<div class="api_metadata"> 335<span>Added in: v0.1.99</span> 336</div> 337<ul> 338<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 339</ul> 340<p>Returns an object containing the address information for a socket. 341For UDP sockets, this object will contain <code>address</code>, <code>family</code> and <code>port</code> 342properties.</p> 343<p>This method throws <code>EBADF</code> if called on an unbound socket.</p> 344<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> 345<div class="api_metadata"> 346<details class="changelog"><summary>History</summary> 347<table> 348<tbody><tr><th>Version</th><th>Changes</th></tr> 349<tr><td>v0.9.1</td> 350<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> 351<tr><td>v0.1.99</td> 352<td><p><span>Added in: v0.1.99</span></p></td></tr> 353</tbody></table> 354</details> 355</div> 356<ul> 357<li><code>port</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 358<li><code>address</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 359<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> 360</ul> 361<p>For UDP sockets, causes the <code>dgram.Socket</code> to listen for datagram 362messages on a named <code>port</code> and optional <code>address</code>. If <code>port</code> is not 363specified or is <code>0</code>, the operating system will attempt to bind to a 364random port. If <code>address</code> is not specified, the operating system will 365attempt to listen on all addresses. Once binding is complete, a 366<code>'listening'</code> event is emitted and the optional <code>callback</code> function is 367called.</p> 368<p>Specifying both a <code>'listening'</code> event listener and passing a 369<code>callback</code> to the <code>socket.bind()</code> method is not harmful but not very 370useful.</p> 371<p>A bound datagram socket keeps the Node.js process running to receive 372datagram messages.</p> 373<p>If binding fails, an <code>'error'</code> event is generated. In rare case (e.g. 374attempting to bind with a closed socket), an <a href="errors.html#errors_class_error"><code>Error</code></a> may be thrown.</p> 375<p>Example of a UDP server listening on port 41234:</p> 376<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>); 377<span class="hljs-keyword">const</span> server = dgram.<span class="hljs-title function_">createSocket</span>(<span class="hljs-string">'udp4'</span>); 378 379server.<span class="hljs-title function_">on</span>(<span class="hljs-string">'error'</span>, <span class="hljs-function">(<span class="hljs-params">err</span>) =></span> { 380 <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">${err.stack}</span>`</span>); 381 server.<span class="hljs-title function_">close</span>(); 382}); 383 384server.<span class="hljs-title function_">on</span>(<span class="hljs-string">'message'</span>, <span class="hljs-function">(<span class="hljs-params">msg, rinfo</span>) =></span> { 385 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`server got: <span class="hljs-subst">${msg}</span> from <span class="hljs-subst">${rinfo.address}</span>:<span class="hljs-subst">${rinfo.port}</span>`</span>); 386}); 387 388server.<span class="hljs-title function_">on</span>(<span class="hljs-string">'listening'</span>, <span class="hljs-function">() =></span> { 389 <span class="hljs-keyword">const</span> address = server.<span class="hljs-title function_">address</span>(); 390 <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>); 391}); 392 393server.<span class="hljs-title function_">bind</span>(<span class="hljs-number">41234</span>); 394<span class="hljs-comment">// Prints: server listening 0.0.0.0:41234</span></code></pre> 395<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> 396<div class="api_metadata"> 397<span>Added in: v0.11.14</span> 398</div> 399<ul> 400<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: 401<ul> 402<li><code>port</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 403<li><code>address</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 404<li><code>exclusive</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 405<li><code>fd</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 406</ul> 407</li> 408<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li> 409</ul> 410<p>For UDP sockets, causes the <code>dgram.Socket</code> to listen for datagram 411messages on a named <code>port</code> and optional <code>address</code> that are passed as 412properties of an <code>options</code> object passed as the first argument. If 413<code>port</code> is not specified or is <code>0</code>, the operating system will attempt 414to bind to a random port. If <code>address</code> is not specified, the operating 415system will attempt to listen on all addresses. Once binding is 416complete, a <code>'listening'</code> event is emitted and the optional <code>callback</code> 417function is called.</p> 418<p>The <code>options</code> object may contain a <code>fd</code> property. When a <code>fd</code> greater 419than <code>0</code> is set, it will wrap around an existing socket with the given 420file descriptor. In this case, the properties of <code>port</code> and <code>address</code> 421will be ignored.</p> 422<p>Specifying both a <code>'listening'</code> event listener and passing a 423<code>callback</code> to the <code>socket.bind()</code> method is not harmful but not very 424useful.</p> 425<p>The <code>options</code> object may contain an additional <code>exclusive</code> property that is 426used when using <code>dgram.Socket</code> objects with the <a href="cluster.html"><code>cluster</code></a> module. When 427<code>exclusive</code> is set to <code>false</code> (the default), cluster workers will use the same 428underlying socket handle allowing connection handling duties to be shared. 429When <code>exclusive</code> is <code>true</code>, however, the handle is not shared and attempted 430port sharing results in an error.</p> 431<p>A bound datagram socket keeps the Node.js process running to receive 432datagram messages.</p> 433<p>If binding fails, an <code>'error'</code> event is generated. In rare case (e.g. 434attempting to bind with a closed socket), an <a href="errors.html#errors_class_error"><code>Error</code></a> may be thrown.</p> 435<p>An example socket listening on an exclusive port is shown below.</p> 436<pre><code class="language-js">socket.<span class="hljs-title function_">bind</span>({ 437 <span class="hljs-attr">address</span>: <span class="hljs-string">'localhost'</span>, 438 <span class="hljs-attr">port</span>: <span class="hljs-number">8000</span>, 439 <span class="hljs-attr">exclusive</span>: <span class="hljs-literal">true</span> 440});</code></pre> 441<h4><code>socket.close([callback])</code><span><a class="mark" href="#dgram_socket_close_callback" id="dgram_socket_close_callback">#</a></span></h4> 442<div class="api_metadata"> 443<span>Added in: v0.1.99</span> 444</div> 445<ul> 446<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> 447</ul> 448<p>Close the underlying socket and stop listening for data on it. If a callback is 449provided, it is added as a listener for the <a href="#dgram_event_close"><code>'close'</code></a> event.</p> 450<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> 451<div class="api_metadata"> 452<span>Added in: v12.0.0</span> 453</div> 454<ul> 455<li><code>port</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 456<li><code>address</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 457<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> 458</ul> 459<p>Associates the <code>dgram.Socket</code> to a remote address and port. Every 460message sent by this handle is automatically sent to that destination. Also, 461the socket will only receive messages from that remote peer. 462Trying to call <code>connect()</code> on an already connected socket will result 463in 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 464provided, <code>'127.0.0.1'</code> (for <code>udp4</code> sockets) or <code>'::1'</code> (for <code>udp6</code> sockets) 465will be used by default. Once the connection is complete, a <code>'connect'</code> event 466is emitted and the optional <code>callback</code> function is called. In case of failure, 467the <code>callback</code> is called or, failing this, an <code>'error'</code> event is emitted.</p> 468<h4><code>socket.disconnect()</code><span><a class="mark" href="#dgram_socket_disconnect" id="dgram_socket_disconnect">#</a></span></h4> 469<div class="api_metadata"> 470<span>Added in: v12.0.0</span> 471</div> 472<p>A synchronous function that disassociates a connected <code>dgram.Socket</code> from 473its remote address. Trying to call <code>disconnect()</code> on an unbound or already 474disconnected socket will result in an <a href="errors.html#errors_err_socket_dgram_not_connected"><code>ERR_SOCKET_DGRAM_NOT_CONNECTED</code></a> 475exception.</p> 476<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> 477<div class="api_metadata"> 478<span>Added in: v0.6.9</span> 479</div> 480<ul> 481<li><code>multicastAddress</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 482<li><code>multicastInterface</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 483</ul> 484<p>Instructs the kernel to leave a multicast group at <code>multicastAddress</code> using the 485<code>IP_DROP_MEMBERSHIP</code> socket option. This method is automatically called by the 486kernel when the socket is closed or the process terminates, so most apps will 487never have reason to call this.</p> 488<p>If <code>multicastInterface</code> is not specified, the operating system will attempt to 489drop membership on all valid interfaces.</p> 490<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> 491<div class="api_metadata"> 492<span>Added in: v13.1.0, v12.16.0</span> 493</div> 494<ul> 495<li><code>sourceAddress</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 496<li><code>groupAddress</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 497<li><code>multicastInterface</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 498</ul> 499<p>Instructs the kernel to leave a source-specific multicast channel at the given 500<code>sourceAddress</code> and <code>groupAddress</code> using the <code>IP_DROP_SOURCE_MEMBERSHIP</code> 501socket option. This method is automatically called by the kernel when the 502socket is closed or the process terminates, so most apps will never have 503reason to call this.</p> 504<p>If <code>multicastInterface</code> is not specified, the operating system will attempt to 505drop membership on all valid interfaces.</p> 506<h4><code>socket.getRecvBufferSize()</code><span><a class="mark" href="#dgram_socket_getrecvbuffersize" id="dgram_socket_getrecvbuffersize">#</a></span></h4> 507<div class="api_metadata"> 508<span>Added in: v8.7.0</span> 509</div> 510<ul> 511<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> 512</ul> 513<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> 514<h4><code>socket.getSendBufferSize()</code><span><a class="mark" href="#dgram_socket_getsendbuffersize" id="dgram_socket_getsendbuffersize">#</a></span></h4> 515<div class="api_metadata"> 516<span>Added in: v8.7.0</span> 517</div> 518<ul> 519<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> 520</ul> 521<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> 522<h4><code>socket.ref()</code><span><a class="mark" href="#dgram_socket_ref" id="dgram_socket_ref">#</a></span></h4> 523<div class="api_metadata"> 524<span>Added in: v0.9.1</span> 525</div> 526<ul> 527<li>Returns: <a href="dgram.html#dgram_class_dgram_socket" class="type"><dgram.Socket></a></li> 528</ul> 529<p>By default, binding a socket will cause it to block the Node.js process from 530exiting as long as the socket is open. The <code>socket.unref()</code> method can be used 531to exclude the socket from the reference counting that keeps the Node.js 532process active. The <code>socket.ref()</code> method adds the socket back to the reference 533counting and restores the default behavior.</p> 534<p>Calling <code>socket.ref()</code> multiples times will have no additional effect.</p> 535<p>The <code>socket.ref()</code> method returns a reference to the socket so calls can be 536chained.</p> 537<h4><code>socket.remoteAddress()</code><span><a class="mark" href="#dgram_socket_remoteaddress" id="dgram_socket_remoteaddress">#</a></span></h4> 538<div class="api_metadata"> 539<span>Added in: v12.0.0</span> 540</div> 541<ul> 542<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 543</ul> 544<p>Returns an object containing the <code>address</code>, <code>family</code>, and <code>port</code> of the remote 545endpoint. This method throws an <a href="errors.html#errors_err_socket_dgram_not_connected"><code>ERR_SOCKET_DGRAM_NOT_CONNECTED</code></a> exception 546if the socket is not connected.</p> 547<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> 548<div class="api_metadata"> 549<details class="changelog"><summary>History</summary> 550<table> 551<tbody><tr><th>Version</th><th>Changes</th></tr> 552<tr><td>v14.5.0</td> 553<td><p>The <code>msg</code> parameter can now be any <code>TypedArray</code> or <code>DataView</code>.</p></td></tr> 554<tr><td>v12.0.0</td> 555<td><p>Added support for sending data on connected sockets.</p></td></tr> 556<tr><td>v8.0.0</td> 557<td><p>The <code>msg</code> parameter can be an <code>Uint8Array</code> now.</p></td></tr> 558<tr><td>v8.0.0</td> 559<td><p>The <code>address</code> parameter is always optional now.</p></td></tr> 560<tr><td>v6.0.0</td> 561<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> 562<tr><td>v5.7.0</td> 563<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> 564<tr><td>v0.1.99</td> 565<td><p><span>Added in: v0.1.99</span></p></td></tr> 566</tbody></table> 567</details> 568</div> 569<ul> 570<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> 571<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> 572<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> 573<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> 574<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> 575<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> 576</ul> 577<p>Broadcasts a datagram on the socket. 578For connectionless sockets, the destination <code>port</code> and <code>address</code> must be 579specified. Connected sockets, on the other hand, will use their associated 580remote endpoint, so the <code>port</code> and <code>address</code> arguments must not be set.</p> 581<p>The <code>msg</code> argument contains the message to be sent. 582Depending on its type, different behavior can apply. If <code>msg</code> is a <code>Buffer</code>, 583any <code>TypedArray</code> or a <code>DataView</code>, 584the <code>offset</code> and <code>length</code> specify the offset within the <code>Buffer</code> where the 585message begins and the number of bytes in the message, respectively. 586If <code>msg</code> is a <code>String</code>, then it is automatically converted to a <code>Buffer</code> 587with <code>'utf8'</code> encoding. With messages that 588contain multi-byte characters, <code>offset</code> and <code>length</code> will be calculated with 589respect to <a href="buffer.html#buffer_static_method_buffer_bytelength_string_encoding">byte length</a> and not the character position. 590If <code>msg</code> is an array, <code>offset</code> and <code>length</code> must not be specified.</p> 591<p>The <code>address</code> argument is a string. If the value of <code>address</code> is a host name, 592DNS will be used to resolve the address of the host. If <code>address</code> is not 593provided or otherwise falsy, <code>'127.0.0.1'</code> (for <code>udp4</code> sockets) or <code>'::1'</code> 594(for <code>udp6</code> sockets) will be used by default.</p> 595<p>If the socket has not been previously bound with a call to <code>bind</code>, the socket 596is assigned a random port number and is bound to the "all interfaces" address 597(<code>'0.0.0.0'</code> for <code>udp4</code> sockets, <code>'::0'</code> for <code>udp6</code> sockets.)</p> 598<p>An optional <code>callback</code> function may be specified to as a way of reporting 599DNS errors or for determining when it is safe to reuse the <code>buf</code> object. 600DNS lookups delay the time to send for at least one tick of the 601Node.js event loop.</p> 602<p>The only way to know for sure that the datagram has been sent is by using a 603<code>callback</code>. If an error occurs and a <code>callback</code> is given, the error will be 604passed as the first argument to the <code>callback</code>. If a <code>callback</code> is not given, 605the error is emitted as an <code>'error'</code> event on the <code>socket</code> object.</p> 606<p>Offset and length are optional but both <em>must</em> be set if either are used. 607They are supported only when the first argument is a <code>Buffer</code>, a <code>TypedArray</code>, 608or a <code>DataView</code>.</p> 609<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> 610<p>Example of sending a UDP packet to a port on <code>localhost</code>;</p> 611<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>); 612<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>); 613<span class="hljs-keyword">const</span> client = dgram.<span class="hljs-title function_">createSocket</span>(<span class="hljs-string">'udp4'</span>); 614client.<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> { 615 client.<span class="hljs-title function_">close</span>(); 616});</code></pre> 617<p>Example of sending a UDP packet composed of multiple buffers to a port on 618<code>127.0.0.1</code>;</p> 619<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>); 620<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>); 621<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>); 622<span class="hljs-keyword">const</span> client = dgram.<span class="hljs-title function_">createSocket</span>(<span class="hljs-string">'udp4'</span>); 623client.<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> { 624 client.<span class="hljs-title function_">close</span>(); 625});</code></pre> 626<p>Sending multiple buffers might be faster or slower depending on the 627application and operating system. Run benchmarks to 628determine the optimal strategy on a case-by-case basis. Generally speaking, 629however, sending multiple buffers is faster.</p> 630<p>Example of sending a UDP packet using a socket connected to a port on 631<code>localhost</code>:</p> 632<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>); 633<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>); 634<span class="hljs-keyword">const</span> client = dgram.<span class="hljs-title function_">createSocket</span>(<span class="hljs-string">'udp4'</span>); 635client.<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> { 636 client.<span class="hljs-title function_">send</span>(message, <span class="hljs-function">(<span class="hljs-params">err</span>) =></span> { 637 client.<span class="hljs-title function_">close</span>(); 638 }); 639});</code></pre> 640<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> 641<p>The maximum size of an IPv4/v6 datagram depends on the <code>MTU</code> 642(Maximum Transmission Unit) and on the <code>Payload Length</code> field size.</p> 643<ul> 644<li> 645<p>The <code>Payload Length</code> field is 16 bits wide, which means that a normal 646payload cannot exceed 64K octets including the internet header and data 647(65,507 bytes = 65,535 − 8 bytes UDP header − 20 bytes IP header); 648this is generally true for loopback interfaces, but such long datagram 649messages are impractical for most hosts and networks.</p> 650</li> 651<li> 652<p>The <code>MTU</code> is the largest size a given link layer technology can support for 653datagram messages. For any link, IPv4 mandates a minimum <code>MTU</code> of 68 654octets, while the recommended <code>MTU</code> for IPv4 is 576 (typically recommended 655as the <code>MTU</code> for dial-up type applications), whether they arrive whole or in 656fragments.</p> 657<p>For IPv6, the minimum <code>MTU</code> is 1280 octets. However, the mandatory minimum 658fragment reassembly buffer size is 1500 octets. The value of 68 octets is 659very small, since most current link layer technologies, like Ethernet, have a 660minimum <code>MTU</code> of 1500.</p> 661</li> 662</ul> 663<p>It is impossible to know in advance the MTU of each link through which 664a packet might travel. Sending a datagram greater than the receiver <code>MTU</code> will 665not work because the packet will get silently dropped without informing the 666source that the data did not reach its intended recipient.</p> 667<h4><code>socket.setBroadcast(flag)</code><span><a class="mark" href="#dgram_socket_setbroadcast_flag" id="dgram_socket_setbroadcast_flag">#</a></span></h4> 668<div class="api_metadata"> 669<span>Added in: v0.6.9</span> 670</div> 671<ul> 672<li><code>flag</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 673</ul> 674<p>Sets or clears the <code>SO_BROADCAST</code> socket option. When set to <code>true</code>, UDP 675packets may be sent to a local interface's broadcast address.</p> 676<p>This method throws <code>EBADF</code> if called on an unbound socket.</p> 677<h4><code>socket.setMulticastInterface(multicastInterface)</code><span><a class="mark" href="#dgram_socket_setmulticastinterface_multicastinterface" id="dgram_socket_setmulticastinterface_multicastinterface">#</a></span></h4> 678<div class="api_metadata"> 679<span>Added in: v8.6.0</span> 680</div> 681<ul> 682<li><code>multicastInterface</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 683</ul> 684<p><em>All references to scope in this section are referring to 685<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 686with a scope index is written as <code>'IP%scope'</code> where scope is an interface name 687or interface number.</em></p> 688<p>Sets the default outgoing multicast interface of the socket to a chosen 689interface or back to system interface selection. The <code>multicastInterface</code> must 690be a valid string representation of an IP from the socket's family.</p> 691<p>For IPv4 sockets, this should be the IP configured for the desired physical 692interface. All packets sent to multicast on the socket will be sent on the 693interface determined by the most recent successful use of this call.</p> 694<p>For IPv6 sockets, <code>multicastInterface</code> should include a scope to indicate the 695interface as in the examples that follow. In IPv6, individual <code>send</code> calls can 696also use explicit scope in addresses, so only packets sent to a multicast 697address without specifying an explicit scope are affected by the most recent 698successful use of this call.</p> 699<p>This method throws <code>EBADF</code> if called on an unbound socket.</p> 700<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> 701<p>On most systems, where scope format uses the interface name:</p> 702<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>); 703 704socket.<span class="hljs-title function_">bind</span>(<span class="hljs-number">1234</span>, <span class="hljs-function">() =></span> { 705 socket.<span class="hljs-title function_">setMulticastInterface</span>(<span class="hljs-string">'::%eth1'</span>); 706});</code></pre> 707<p>On Windows, where scope format uses an interface number:</p> 708<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>); 709 710socket.<span class="hljs-title function_">bind</span>(<span class="hljs-number">1234</span>, <span class="hljs-function">() =></span> { 711 socket.<span class="hljs-title function_">setMulticastInterface</span>(<span class="hljs-string">'::%2'</span>); 712});</code></pre> 713<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> 714<p>All systems use an IP of the host on the desired physical interface:</p> 715<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>); 716 717socket.<span class="hljs-title function_">bind</span>(<span class="hljs-number">1234</span>, <span class="hljs-function">() =></span> { 718 socket.<span class="hljs-title function_">setMulticastInterface</span>(<span class="hljs-string">'10.0.0.2'</span>); 719});</code></pre> 720<h5>Call results<span><a class="mark" href="#dgram_call_results" id="dgram_call_results">#</a></span></h5> 721<p>A call on a socket that is not ready to send or no longer open may throw a <em>Not 722running</em> <a href="errors.html#errors_class_error"><code>Error</code></a>.</p> 723<p>If <code>multicastInterface</code> can not be parsed into an IP then an <em>EINVAL</em> 724<a href="errors.html#errors_class_systemerror"><code>System Error</code></a> is thrown.</p> 725<p>On IPv4, if <code>multicastInterface</code> is a valid address but does not match any 726interface, or if the address does not match the family then 727a <a href="errors.html#errors_class_systemerror"><code>System Error</code></a> such as <code>EADDRNOTAVAIL</code> or <code>EPROTONOSUP</code> is thrown.</p> 728<p>On IPv6, most errors with specifying or omitting scope will result in the socket 729continuing to use (or returning to) the system's default interface selection.</p> 730<p>A socket's address family's ANY address (IPv4 <code>'0.0.0.0'</code> or IPv6 <code>'::'</code>) can be 731used to return control of the sockets default outgoing interface to the system 732for future multicast packets.</p> 733<h4><code>socket.setMulticastLoopback(flag)</code><span><a class="mark" href="#dgram_socket_setmulticastloopback_flag" id="dgram_socket_setmulticastloopback_flag">#</a></span></h4> 734<div class="api_metadata"> 735<span>Added in: v0.3.8</span> 736</div> 737<ul> 738<li><code>flag</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 739</ul> 740<p>Sets or clears the <code>IP_MULTICAST_LOOP</code> socket option. When set to <code>true</code>, 741multicast packets will also be received on the local interface.</p> 742<p>This method throws <code>EBADF</code> if called on an unbound socket.</p> 743<h4><code>socket.setMulticastTTL(ttl)</code><span><a class="mark" href="#dgram_socket_setmulticastttl_ttl" id="dgram_socket_setmulticastttl_ttl">#</a></span></h4> 744<div class="api_metadata"> 745<span>Added in: v0.3.8</span> 746</div> 747<ul> 748<li><code>ttl</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 749</ul> 750<p>Sets the <code>IP_MULTICAST_TTL</code> socket option. While TTL generally stands for 751"Time to Live", in this context it specifies the number of IP hops that a 752packet is allowed to travel through, specifically for multicast traffic. Each 753router or gateway that forwards a packet decrements the TTL. If the TTL is 754decremented to 0 by a router, it will not be forwarded.</p> 755<p>The <code>ttl</code> argument may be between 0 and 255. The default on most systems is <code>1</code>.</p> 756<p>This method throws <code>EBADF</code> if called on an unbound socket.</p> 757<h4><code>socket.setRecvBufferSize(size)</code><span><a class="mark" href="#dgram_socket_setrecvbuffersize_size" id="dgram_socket_setrecvbuffersize_size">#</a></span></h4> 758<div class="api_metadata"> 759<span>Added in: v8.7.0</span> 760</div> 761<ul> 762<li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 763</ul> 764<p>Sets the <code>SO_RCVBUF</code> socket option. Sets the maximum socket receive buffer 765in bytes.</p> 766<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> 767<h4><code>socket.setSendBufferSize(size)</code><span><a class="mark" href="#dgram_socket_setsendbuffersize_size" id="dgram_socket_setsendbuffersize_size">#</a></span></h4> 768<div class="api_metadata"> 769<span>Added in: v8.7.0</span> 770</div> 771<ul> 772<li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 773</ul> 774<p>Sets the <code>SO_SNDBUF</code> socket option. Sets the maximum socket send buffer 775in bytes.</p> 776<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> 777<h4><code>socket.setTTL(ttl)</code><span><a class="mark" href="#dgram_socket_setttl_ttl" id="dgram_socket_setttl_ttl">#</a></span></h4> 778<div class="api_metadata"> 779<span>Added in: v0.1.101</span> 780</div> 781<ul> 782<li><code>ttl</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> 783</ul> 784<p>Sets the <code>IP_TTL</code> socket option. While TTL generally stands for "Time to Live", 785in this context it specifies the number of IP hops that a packet is allowed to 786travel through. Each router or gateway that forwards a packet decrements the 787TTL. If the TTL is decremented to 0 by a router, it will not be forwarded. 788Changing TTL values is typically done for network probes or when multicasting.</p> 789<p>The <code>ttl</code> argument may be between between 1 and 255. The default on most systems 790is 64.</p> 791<p>This method throws <code>EBADF</code> if called on an unbound socket.</p> 792<h4><code>socket.unref()</code><span><a class="mark" href="#dgram_socket_unref" id="dgram_socket_unref">#</a></span></h4> 793<div class="api_metadata"> 794<span>Added in: v0.9.1</span> 795</div> 796<ul> 797<li>Returns: <a href="dgram.html#dgram_class_dgram_socket" class="type"><dgram.Socket></a></li> 798</ul> 799<p>By default, binding a socket will cause it to block the Node.js process from 800exiting as long as the socket is open. The <code>socket.unref()</code> method can be used 801to exclude the socket from the reference counting that keeps the Node.js 802process active, allowing the process to exit even if the socket is still 803listening.</p> 804<p>Calling <code>socket.unref()</code> multiple times will have no addition effect.</p> 805<p>The <code>socket.unref()</code> method returns a reference to the socket so calls can be 806chained.</p> 807</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> 808<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> 809<div class="api_metadata"> 810<details class="changelog"><summary>History</summary> 811<table> 812<tbody><tr><th>Version</th><th>Changes</th></tr> 813<tr><td>v14.17.0</td> 814<td><p>AbortSignal support was added.</p></td></tr> 815<tr><td>v11.4.0</td> 816<td><p>The <code>ipv6Only</code> option is supported.</p></td></tr> 817<tr><td>v8.7.0</td> 818<td><p>The <code>recvBufferSize</code> and <code>sendBufferSize</code> options are supported now.</p></td></tr> 819<tr><td>v8.6.0</td> 820<td><p>The <code>lookup</code> option is supported.</p></td></tr> 821<tr><td>v0.11.13</td> 822<td><p><span>Added in: v0.11.13</span></p></td></tr> 823</tbody></table> 824</details> 825</div> 826<ul> 827<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: 828<ul> 829<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>. 830Required.</li> 831<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 832address, even if another process has already bound a socket on it. 833<strong>Default:</strong> <code>false</code>.</li> 834<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 835disable dual-stack support, i.e., binding to address <code>::</code> won't make 836<code>0.0.0.0</code> be bound. <strong>Default:</strong> <code>false</code>.</li> 837<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> 838<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> 839<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> 840<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> 841</ul> 842</li> 843<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> 844<li>Returns: <a href="dgram.html#dgram_class_dgram_socket" class="type"><dgram.Socket></a></li> 845</ul> 846<p>Creates a <code>dgram.Socket</code> object. Once the socket is created, calling 847<a href="#dgram_socket_bind_port_address_callback"><code>socket.bind()</code></a> will instruct the socket to begin listening for datagram 848messages. 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 849method will bind the socket to the "all interfaces" address on a random port 850(it does the right thing for both <code>udp4</code> and <code>udp6</code> sockets). The bound address 851and port can be retrieved using <a href="#dgram_socket_address"><code>socket.address().address</code></a> and 852<a href="#dgram_socket_address"><code>socket.address().port</code></a>.</p> 853<p>If the <code>signal</code> option is enabled, calling <code>.abort()</code> on the corresponding 854<code>AbortController</code> is similar to calling <code>.close()</code> on the socket:</p> 855<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>(); 856<span class="hljs-keyword">const</span> { signal } = controller; 857<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 }); 858server.<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> { 859 <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>); 860}); 861<span class="hljs-comment">// Later, when you want to close the server.</span> 862controller.<span class="hljs-title function_">abort</span>();</code></pre> 863<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> 864<div class="api_metadata"> 865<span>Added in: v0.1.99</span> 866</div> 867<ul> 868<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> 869<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> 870<li>Returns: <a href="dgram.html#dgram_class_dgram_socket" class="type"><dgram.Socket></a></li> 871</ul> 872<p>Creates a <code>dgram.Socket</code> object of the specified <code>type</code>.</p> 873<p>Once the socket is created, calling <a href="#dgram_socket_bind_port_address_callback"><code>socket.bind()</code></a> will instruct the 874socket to begin listening for datagram messages. When <code>address</code> and <code>port</code> are 875not passed to <a href="#dgram_socket_bind_port_address_callback"><code>socket.bind()</code></a> the method will bind the socket to the "all 876interfaces" address on a random port (it does the right thing for both <code>udp4</code> 877and <code>udp6</code> sockets). The bound address and port can be retrieved using 878<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> 879 <!-- API END --> 880 </div> 881 </div> 882 </div> 883 <script> 884 'use strict'; 885 { 886 const kCustomPreference = 'customDarkTheme'; 887 const userSettings = sessionStorage.getItem(kCustomPreference); 888 const themeToggleButton = document.getElementById('theme-toggle-btn'); 889 if (userSettings === null && window.matchMedia) { 890 const mq = window.matchMedia('(prefers-color-scheme: dark)'); 891 if ('onchange' in mq) { 892 function mqChangeListener(e) { 893 document.body.classList.toggle('dark-mode', e.matches); 894 } 895 mq.addEventListener('change', mqChangeListener); 896 if (themeToggleButton) { 897 themeToggleButton.addEventListener('click', function() { 898 mq.removeEventListener('change', mqChangeListener); 899 }, { once: true }); 900 } 901 } 902 if (mq.matches) { 903 document.body.classList.add('dark-mode'); 904 } 905 } else if (userSettings === 'true') { 906 document.body.classList.add('dark-mode'); 907 } 908 if (themeToggleButton) { 909 themeToggleButton.hidden = false; 910 themeToggleButton.addEventListener('click', function() { 911 sessionStorage.setItem( 912 kCustomPreference, 913 document.body.classList.toggle('dark-mode') 914 ); 915 }); 916 } 917 } 918 </script> 919</body> 920</html> 921