<?xml version="1.0" encoding="utf-8" ?> <!DOCTYPE erlref SYSTEM "erlref.dtd"> <erlref> <header> <copyright> <year>1997</year><year>2013</year> <holder>Ericsson AB. All Rights Reserved.</holder> </copyright> <legalnotice> The contents of this file are subject to the Erlang Public License, Version 1.1, (the "License"); you may not use this file except in compliance with the License. You should have received a copy of the Erlang Public License along with this software. If not, it can be retrieved online at http://www.erlang.org/. Software distributed under the License is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for the specific language governing rights and limitations under the License. </legalnotice> <title>gen_udp</title> <prepared>tony@erix.ericsson.se</prepared> <docno></docno> <date>1997-12-03</date> <rev>A</rev> </header> <module>gen_udp</module> <modulesummary>Interface to UDP sockets</modulesummary> <description> <p>The <c>gen_udp</c> module provides functions for communicating with sockets using the UDP protocol.</p> </description> <datatypes> <datatype> <name name="option"/> </datatype> <datatype> <name name="option_name"/> </datatype> <datatype> <name><marker id="type-socket">socket()</marker></name> <desc> <p>As returned by open/1,2.</p> </desc> </datatype> </datatypes> <funcs> <func> <name name="open" arity="1"/> <name name="open" arity="2"/> <fsummary>Associate a UDP port number with the process calling it</fsummary> <desc> <p>Associates a UDP port number (<c><anno>Port</anno></c>) with the calling process.</p> <p>The available options are:</p> <taglist> <tag><c>list</c></tag> <item> <p>Received <c>Packet</c> is delivered as a list.</p> </item> <tag><c>binary</c></tag> <item> <p>Received <c>Packet</c> is delivered as a binary.</p> </item> <tag><c>{ip, ip_address()}</c></tag> <item> <p>If the host has several network interfaces, this option specifies which one to use.</p> </item> <tag><c>{ifaddr, ip_address()}</c></tag> <item> <p>Same as <c>{ip, ip_address()}</c>. If the host has several network interfaces, this option specifies which one to use.</p> </item> <tag><c>{fd, integer() >= 0}</c></tag> <item> <p>If a socket has somehow been opened without using <c>gen_udp</c>, use this option to pass the file descriptor for it.</p> </item> <tag><c>inet6</c></tag> <item> <p>Set up the socket for IPv6.</p> </item> <tag><c>inet</c></tag> <item> <p>Set up the socket for IPv4.</p> </item> <tag><c>{udp_module, module()}</c></tag> <item> <p> Override which callback module is used. Defaults to <c>inet_udp</c> for IPv4 and <c>inet6_udp</c> for IPv6. </p> </item> <tag><c>{multicast_if, Address}</c></tag> <item> <p>Set the local device for a multicast socket.</p> </item> <tag><c>{multicast_loop, true | false}</c></tag> <item> <p> When <c>true</c> sent multicast packets will be looped back to the local sockets. </p> </item> <tag><c>{multicast_ttl, Integer}</c></tag> <item> <p> The <c>multicast_ttl</c> option changes the time-to-live (TTL) for outgoing multicast datagrams in order to control the scope of the multicasts. </p> <p> Datagrams with a TTL of 1 are not forwarded beyond the local network. <br />Default: 1 </p> </item> <tag><c>{add_membership, {MultiAddress, InterfaceAddress}}</c></tag> <item> <p>Join a multicast group. </p> </item> <tag><c>{drop_membership, {MultiAddress, InterfaceAddress}}</c></tag> <item> <p>Leave multicast group.</p> </item> <tag><c>Opt</c></tag> <item> <p>See <seealso marker="inet#setopts/2">inet:setopts/2</seealso>.</p> </item> </taglist> <p>The returned socket <c><anno>Socket</anno></c> is used to send packets from this port with <c>send/4</c>. When UDP packets arrive at the opened port, if the socket is in an active mode the packets are delivered as messages to the controlling process:</p> <code type="none"> {udp, Socket, IP, InPortNo, Packet}</code> <p>If the socket is not in an active mode, data can be retrieved via the <seealso marker="#recv/2">recv/2,3</seealso> calls. Note that arriving UDP packets that are longer than the receive buffer option specifies, might be truncated without warning.</p> <p>When a socket in <c>{active, N}</c> mode (see <seealso marker="inet#setopts/2"> inet:setopts/2</seealso> for details) transitions to passive (<c>{active, false}</c>) mode, the controlling process is notified by a message of the following form:</p> <code type="none"> {udp_passive, Socket}</code> <p><c>IP</c> and <c>InPortNo</c> define the address from which <c>Packet</c> came. <c>Packet</c> is a list of bytes if the option <c>list</c> was specified. <c>Packet</c> is a binary if the option <c>binary</c> was specified.</p> <p>Default value for the receive buffer option is <c>{recbuf, 8192}</c>.</p> <p>If <c><anno>Port</anno> == 0</c>, the underlying OS assigns a free UDP port, use <c>inet:port/1</c> to retrieve it.</p> </desc> </func> <func> <name name="send" arity="4"/> <fsummary>Send a packet</fsummary> <desc> <p>Sends a packet to the specified address and port. The <c><anno>Address</anno></c> argument can be either a hostname, or an IP address.</p> </desc> </func> <func> <name name="recv" arity="2"/> <name name="recv" arity="3"/> <fsummary>Receive a packet from a passive socket</fsummary> <desc> <p>This function receives a packet from a socket in passive mode.</p> <p>The optional <c><anno>Timeout</anno></c> parameter specifies a timeout in milliseconds. The default value is <c>infinity</c>.</p> </desc> </func> <func> <name name="controlling_process" arity="2"/> <fsummary>Change controlling process of a socket</fsummary> <desc> <p>Assigns a new controlling process <c><anno>Pid</anno></c> to <c><anno>Socket</anno></c>. The controlling process is the process which receives messages from the socket. If called by any other process than the current controlling process, <c>{error, not_owner}</c> is returned.</p> </desc> </func> <func> <name name="close" arity="1"/> <fsummary>Close a UDP socket</fsummary> <desc> <p>Closes a UDP socket.</p> </desc> </func> </funcs> </erlref>