| Server IP : 79.136.114.73 / Your IP : 3.147.43.250 Web Server : Apache/2.4.7 (Ubuntu) PHP/5.5.9-1ubuntu4.29 OpenSSL/1.0.1f System : Linux b8009 3.13.0-170-generic #220-Ubuntu SMP Thu May 9 12:40:49 UTC 2019 x86_64 User : www-data ( 33) PHP Version : 5.5.9-1ubuntu4.29 Disable Function : pcntl_alarm,pcntl_fork,pcntl_waitpid,pcntl_wait,pcntl_wifexited,pcntl_wifstopped,pcntl_wifsignaled,pcntl_wexitstatus,pcntl_wtermsig,pcntl_wstopsig,pcntl_signal,pcntl_signal_dispatch,pcntl_get_last_error,pcntl_strerror,pcntl_sigprocmask,pcntl_sigwaitinfo,pcntl_sigtimedwait,pcntl_exec,pcntl_getpriority,pcntl_setpriority, MySQL : ON | cURL : ON | WGET : ON | Perl : ON | Python : ON | Sudo : ON | Pkexec : ON Directory : /usr/share/doc/nodejs/api/ |
Upload File : |
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>UDP / Datagram Sockets Node.js v0.10.25 Manual & Documentation</title>
<link rel="stylesheet" href="assets/style.css">
<link rel="stylesheet" href="assets/sh.css">
<link rel="canonical" href="http://nodejs.org/api/dgram.html">
</head>
<body class="alt apidoc" id="api-section-dgram">
<div id="intro" class="interior">
<a href="/" title="Go back to the home page">
<img id="logo" src="http://nodejs.org/images/logo-light.png" alt="node.js">
</a>
</div>
<div id="content" class="clearfix">
<div id="column2" class="interior">
<ul>
<li><a href="/" class="home">Home</a></li>
<li><a href="/download/" class="download">Download</a></li>
<li><a href="/about/" class="about">About</a></li>
<li><a href="http://npmjs.org/" class="npm">npm Registry</a></li>
<li><a href="http://nodejs.org/api/" class="docs current">Docs</a></li>
<li><a href="http://blog.nodejs.org" class="blog">Blog</a></li>
<li><a href="/community/" class="community">Community</a></li>
<li><a href="/logos/" class="logos">Logos</a></li>
<li><a href="http://jobs.nodejs.org/" class="jobs">Jobs</a></li>
</ul>
<p class="twitter"><a href="http://twitter.com/nodejs">@nodejs</a></p>
</div>
<div id="column1" class="interior">
<header>
<h1>Node.js v0.10.25 Manual & Documentation</h1>
<div id="gtoc">
<p>
<a href="index.html" name="toc">Index</a> |
<a href="all.html">View on single page</a> |
<a href="dgram.json">View as JSON</a>
</p>
</div>
<hr>
</header>
<div id="toc">
<h2>Table of Contents</h2>
<ul>
<li><a href="#dgram_udp_datagram_sockets">UDP / Datagram Sockets</a><ul>
<li><a href="#dgram_dgram_createsocket_type_callback">dgram.createSocket(type, [callback])</a></li>
<li><a href="#dgram_class_dgram_socket">Class: dgram.Socket</a><ul>
<li><a href="#dgram_event_message">Event: 'message'</a></li>
<li><a href="#dgram_event_listening">Event: 'listening'</a></li>
<li><a href="#dgram_event_close">Event: 'close'</a></li>
<li><a href="#dgram_event_error">Event: 'error'</a></li>
<li><a href="#dgram_socket_send_buf_offset_length_port_address_callback">socket.send(buf, offset, length, port, address, [callback])</a></li>
<li><a href="#dgram_socket_bind_port_address_callback">socket.bind(port, [address], [callback])</a></li>
<li><a href="#dgram_socket_close">socket.close()</a></li>
<li><a href="#dgram_socket_address">socket.address()</a></li>
<li><a href="#dgram_socket_setbroadcast_flag">socket.setBroadcast(flag)</a></li>
<li><a href="#dgram_socket_setttl_ttl">socket.setTTL(ttl)</a></li>
<li><a href="#dgram_socket_setmulticastttl_ttl">socket.setMulticastTTL(ttl)</a></li>
<li><a href="#dgram_socket_setmulticastloopback_flag">socket.setMulticastLoopback(flag)</a></li>
<li><a href="#dgram_socket_addmembership_multicastaddress_multicastinterface">socket.addMembership(multicastAddress, [multicastInterface])</a></li>
<li><a href="#dgram_socket_dropmembership_multicastaddress_multicastinterface">socket.dropMembership(multicastAddress, [multicastInterface])</a></li>
<li><a href="#dgram_socket_unref">socket.unref()</a></li>
<li><a href="#dgram_socket_ref">socket.ref()</a></li>
</ul>
</li>
</ul>
</li>
</ul>
</div>
<div id="apicontent">
<h1>UDP / Datagram Sockets<span><a class="mark" href="#dgram_udp_datagram_sockets" id="dgram_udp_datagram_sockets">#</a></span></h1>
<pre class="api_stability_3">Stability: 3 - Stable</pre><!-- name=dgram -->
<p>Datagram sockets are available through <code>require('dgram')</code>.
</p>
<p>Important note: the behavior of <code>dgram.Socket#bind()</code> has changed in v0.10
and is always asynchronous now. If you have code that looks like this:
</p>
<pre><code>var s = dgram.createSocket('udp4');
s.bind(1234);
s.addMembership('224.0.0.114');</code></pre>
<p>You have to change it to this:
</p>
<pre><code>var s = dgram.createSocket('udp4');
s.bind(1234, function() {
s.addMembership('224.0.0.114');
});</code></pre>
<h2>dgram.createSocket(type, [callback])<span><a class="mark" href="#dgram_dgram_createsocket_type_callback" id="dgram_dgram_createsocket_type_callback">#</a></span></h2>
<div class="signature"><ul>
<li><code>type</code> String. Either 'udp4' or 'udp6'</li>
<li><code>callback</code> Function. Attached as a listener to <code>message</code> events.
Optional</li>
<li>Returns: Socket object</li>
</div></ul>
<p>Creates a datagram Socket of the specified types. Valid types are <code>udp4</code>
and <code>udp6</code>.
</p>
<p>Takes an optional callback which is added as a listener for <code>message</code> events.
</p>
<p>Call <code>socket.bind</code> if you want to receive datagrams. <code>socket.bind()</code> will bind
to the "all interfaces" address on a random port (it does the right thing for
both <code>udp4</code> and <code>udp6</code> sockets). You can then retrieve the address and port
with <code>socket.address().address</code> and <code>socket.address().port</code>.
</p>
<h2>Class: dgram.Socket<span><a class="mark" href="#dgram_class_dgram_socket" id="dgram_class_dgram_socket">#</a></span></h2>
<p>The dgram Socket class encapsulates the datagram functionality. It
should be created via <code>dgram.createSocket(type, [callback])</code>.
</p>
<h3>Event: 'message'<span><a class="mark" href="#dgram_event_message" id="dgram_event_message">#</a></span></h3>
<div class="signature"><ul>
<li><code>msg</code> Buffer object. The message</li>
<li><code>rinfo</code> Object. Remote address information</li>
</div></ul>
<p>Emitted when a new datagram is available on a socket. <code>msg</code> is a <code>Buffer</code> and <code>rinfo</code> is
an object with the sender's address information and the number of bytes in the datagram.
</p>
<h3>Event: 'listening'<span><a class="mark" href="#dgram_event_listening" id="dgram_event_listening">#</a></span></h3>
<p>Emitted when a socket starts listening for datagrams. This happens as soon as UDP sockets
are created.
</p>
<h3>Event: 'close'<span><a class="mark" href="#dgram_event_close" id="dgram_event_close">#</a></span></h3>
<p>Emitted when a socket is closed with <code>close()</code>. No new <code>message</code> events will be emitted
on this socket.
</p>
<h3>Event: 'error'<span><a class="mark" href="#dgram_event_error" id="dgram_event_error">#</a></span></h3>
<div class="signature"><ul>
<li><code>exception</code> Error object</li>
</div></ul>
<p>Emitted when an error occurs.
</p>
<h3>socket.send(buf, offset, length, port, address, [callback])<span><a class="mark" href="#dgram_socket_send_buf_offset_length_port_address_callback" id="dgram_socket_send_buf_offset_length_port_address_callback">#</a></span></h3>
<div class="signature"><ul>
<li><code>buf</code> Buffer object. Message to be sent</li>
<li><code>offset</code> Integer. Offset in the buffer where the message starts.</li>
<li><code>length</code> Integer. Number of bytes in the message.</li>
<li><code>port</code> Integer. Destination port.</li>
<li><code>address</code> String. Destination hostname or IP address.</li>
<li><code>callback</code> Function. Called when the message has been sent. Optional.</li>
</div></ul>
<p>For UDP sockets, the destination port and address must be specified. A string
may be supplied for the <code>address</code> parameter, and it will be resolved with DNS.
</p>
<p>If the address is omitted or is an empty string, <code>'0.0.0.0'</code> or <code>'::0'</code> is used
instead. Depending on the network configuration, those defaults may or may not
work; it's best to be explicit about the destination address.
</p>
<p>If the socket has not been previously bound with a call to <code>bind</code>, it gets
assigned a random port number and is bound to the "all interfaces" address
(<code>'0.0.0.0'</code> for <code>udp4</code> sockets, <code>'::0'</code> for <code>udp6</code> sockets.)
</p>
<p>An optional callback may be specified to detect DNS errors or for determining
when it's safe to reuse the <code>buf</code> object. Note that DNS lookups delay the time
to send for at least one tick. The only way to know for sure that the datagram
has been sent is by using a callback.
</p>
<p>Example of sending a UDP packet to a random port on <code>localhost</code>;
</p>
<pre><code>var dgram = require('dgram');
var message = new Buffer("Some bytes");
var client = dgram.createSocket("udp4");
client.send(message, 0, message.length, 41234, "localhost", function(err, bytes) {
client.close();
});</code></pre>
<p><strong>A Note about UDP datagram size</strong>
</p>
<p>The maximum size of an <code>IPv4/v6</code> datagram depends on the <code>MTU</code> (<em>Maximum Transmission Unit</em>)
and on the <code>Payload Length</code> field size.
</p>
<ul>
<li><p>The <code>Payload Length</code> field is <code>16 bits</code> wide, which means that a normal payload
cannot be larger than 64K octets including internet header and data
(65,507 bytes = 65,535 − 8 bytes UDP header − 20 bytes IP header);
this is generally true for loopback interfaces, but such long datagrams
are impractical for most hosts and networks.</p>
</li>
<li><p>The <code>MTU</code> is the largest size a given link layer technology can support for datagrams.
For any link, <code>IPv4</code> mandates a minimum <code>MTU</code> of <code>68</code> octets, while the recommended <code>MTU</code>
for IPv4 is <code>576</code> (typically recommended as the <code>MTU</code> for dial-up type applications),
whether they arrive whole or in fragments.</p>
<p>For <code>IPv6</code>, the minimum <code>MTU</code> is <code>1280</code> octets, however, the mandatory minimum
fragment reassembly buffer size is <code>1500</code> octets.
The value of <code>68</code> octets is very small, since most current link layer technologies have
a minimum <code>MTU</code> of <code>1500</code> (like Ethernet).</p>
</li>
</ul>
<p>Note that it's impossible to know in advance the MTU of each link through which
a packet might travel, and that generally sending a datagram greater than
the (receiver) <code>MTU</code> won't work (the packet gets silently dropped, without
informing the source that the data did not reach its intended recipient).
</p>
<h3>socket.bind(port, [address], [callback])<span><a class="mark" href="#dgram_socket_bind_port_address_callback" id="dgram_socket_bind_port_address_callback">#</a></span></h3>
<div class="signature"><ul>
<li><code>port</code> Integer</li>
<li><code>address</code> String, Optional</li>
<li><code>callback</code> Function with no parameters, Optional. Callback when
binding is done.</li>
</div></ul>
<p>For UDP sockets, listen for datagrams on a named <code>port</code> and optional
<code>address</code>. If <code>address</code> is not specified, the OS will try to listen on
all addresses. After binding is done, a "listening" event is emitted
and the <code>callback</code>(if specified) is called. Specifying both a
"listening" event listener and <code>callback</code> is not harmful but not very
useful.
</p>
<p>A bound datagram socket keeps the node process running to receive
datagrams.
</p>
<p>If binding fails, an "error" event is generated. In rare case (e.g.
binding a closed socket), an <code>Error</code> may be thrown by this method.
</p>
<p>Example of a UDP server listening on port 41234:
</p>
<pre><code>var dgram = require("dgram");
var server = dgram.createSocket("udp4");
server.on("error", function (err) {
console.log("server error:\n" + err.stack);
server.close();
});
server.on("message", function (msg, rinfo) {
console.log("server got: " + msg + " from " +
rinfo.address + ":" + rinfo.port);
});
server.on("listening", function () {
var address = server.address();
console.log("server listening " +
address.address + ":" + address.port);
});
server.bind(41234);
// server listening 0.0.0.0:41234</code></pre>
<h3>socket.close()<span><a class="mark" href="#dgram_socket_close" id="dgram_socket_close">#</a></span></h3>
<p>Close the underlying socket and stop listening for data on it.
</p>
<h3>socket.address()<span><a class="mark" href="#dgram_socket_address" id="dgram_socket_address">#</a></span></h3>
<p>Returns an object containing the address information for a socket. For UDP sockets,
this object will contain <code>address</code> , <code>family</code> and <code>port</code>.
</p>
<h3>socket.setBroadcast(flag)<span><a class="mark" href="#dgram_socket_setbroadcast_flag" id="dgram_socket_setbroadcast_flag">#</a></span></h3>
<div class="signature"><ul>
<li><code>flag</code> Boolean</li>
</div></ul>
<p>Sets or clears the <code>SO_BROADCAST</code> socket option. When this option is set, UDP packets
may be sent to a local interface's broadcast address.
</p>
<h3>socket.setTTL(ttl)<span><a class="mark" href="#dgram_socket_setttl_ttl" id="dgram_socket_setttl_ttl">#</a></span></h3>
<div class="signature"><ul>
<li><code>ttl</code> Integer</li>
</div></ul>
<p>Sets the <code>IP_TTL</code> socket option. TTL stands for "Time to Live," but in this context it
specifies the number of IP hops that a packet is allowed to go through. Each router or
gateway that forwards a packet decrements the TTL. If the TTL is decremented to 0 by a
router, it will not be forwarded. Changing TTL values is typically done for network
probes or when multicasting.
</p>
<p>The argument to <code>setTTL()</code> is a number of hops between 1 and 255. The default on most
systems is 64.
</p>
<h3>socket.setMulticastTTL(ttl)<span><a class="mark" href="#dgram_socket_setmulticastttl_ttl" id="dgram_socket_setmulticastttl_ttl">#</a></span></h3>
<div class="signature"><ul>
<li><code>ttl</code> Integer</li>
</div></ul>
<p>Sets the <code>IP_MULTICAST_TTL</code> socket option. TTL stands for "Time to Live," but in this
context it specifies the number of IP hops that a packet is allowed to go through,
specifically for multicast traffic. Each router or gateway that forwards a packet
decrements the TTL. If the TTL is decremented to 0 by a router, it will not be forwarded.
</p>
<p>The argument to <code>setMulticastTTL()</code> is a number of hops between 0 and 255. The default on most
systems is 1.
</p>
<h3>socket.setMulticastLoopback(flag)<span><a class="mark" href="#dgram_socket_setmulticastloopback_flag" id="dgram_socket_setmulticastloopback_flag">#</a></span></h3>
<div class="signature"><ul>
<li><code>flag</code> Boolean</li>
</div></ul>
<p>Sets or clears the <code>IP_MULTICAST_LOOP</code> socket option. When this option is set, multicast
packets will also be received on the local interface.
</p>
<h3>socket.addMembership(multicastAddress, [multicastInterface])<span><a class="mark" href="#dgram_socket_addmembership_multicastaddress_multicastinterface" id="dgram_socket_addmembership_multicastaddress_multicastinterface">#</a></span></h3>
<div class="signature"><ul>
<li><code>multicastAddress</code> String</li>
<li><code>multicastInterface</code> String, Optional</li>
</div></ul>
<p>Tells the kernel to join a multicast group with <code>IP_ADD_MEMBERSHIP</code> socket option.
</p>
<p>If <code>multicastInterface</code> is not specified, the OS will try to add membership to all valid
interfaces.
</p>
<h3>socket.dropMembership(multicastAddress, [multicastInterface])<span><a class="mark" href="#dgram_socket_dropmembership_multicastaddress_multicastinterface" id="dgram_socket_dropmembership_multicastaddress_multicastinterface">#</a></span></h3>
<div class="signature"><ul>
<li><code>multicastAddress</code> String</li>
<li><code>multicastInterface</code> String, Optional</li>
</div></ul>
<p>Opposite of <code>addMembership</code> - tells the kernel to leave a multicast group with
<code>IP_DROP_MEMBERSHIP</code> socket option. This is automatically called by the kernel
when the socket is closed or process terminates, so most apps will never need to call
this.
</p>
<p>If <code>multicastInterface</code> is not specified, the OS will try to drop membership to all valid
interfaces.
</p>
<h3>socket.unref()<span><a class="mark" href="#dgram_socket_unref" id="dgram_socket_unref">#</a></span></h3>
<p>Calling <code>unref</code> on a socket will allow the program to exit if this is the only
active socket in the event system. If the socket is already <code>unref</code>d calling
<code>unref</code> again will have no effect.
</p>
<h3>socket.ref()<span><a class="mark" href="#dgram_socket_ref" id="dgram_socket_ref">#</a></span></h3>
<p>Opposite of <code>unref</code>, calling <code>ref</code> on a previously <code>unref</code>d socket will <em>not</em>
let the program exit if it's the only socket left (the default behavior). If
the socket is <code>ref</code>d calling <code>ref</code> again will have no effect.
</p>
</div>
</div>
</div>
<div id="footer">
<a href="http://joyent.com" class="joyent-logo">Joyent</a>
<ul class="clearfix">
<li><a href="/">Node.js</a></li>
<li><a href="/download/">Download</a></li>
<li><a href="/about/">About</a></li>
<li><a href="http://npmjs.org/">npm Registry</a></li>
<li><a href="http://nodejs.org/api/">Docs</a></li>
<li><a href="http://blog.nodejs.org">Blog</a></li>
<li><a href="/community/">Community</a></li>
<li><a href="/logos/">Logos</a></li>
<li><a href="http://jobs.nodejs.org/">Jobs</a></li>
<li><a href="http://twitter.com/nodejs" class="twitter">@nodejs</a></li>
</ul>
<p>Copyright <a href="http://joyent.com/">Joyent, Inc</a>, Node.js is a <a href="/trademark-policy.pdf">trademark</a> of Joyent, Inc. View <a href="https://raw.github.com/joyent/node/v0.10.25/LICENSE">license</a>.</p>
</div>
</body>
</html>