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<!DOCTYPE erlref SYSTEM "erlref.dtd">
<erlref>
<header>
<copyright>
<year>1997</year><year>2013</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
</legalnotice>
<title>gen_udp</title>
<prepared>[email protected]</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>socket()</name>
<desc>
<p><marker id="type-socket"/>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. If <c><anno>Port</anno></c> is not set to 0
and/or <c>{ip, ip_address()}</c> is combined with this option
the fd will be bound to the given interface and port after being
opened. If these options are not given it is assumed that the fd
is already bound appropriately.
</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>local</c></tag>
<item>
<p>Set up the socket for local address family. This option is only
valid together with <c>{fd, integer()}</c> when the file descriptor
is of local address family (e.g. a Unix Domain Socket)</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>
