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<!DOCTYPE erlref SYSTEM "erlref.dtd">

<erlref>
  <header>
    <copyright>
      <year>1997</year><year>2012</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, they are delivered as messages:</p>
        <code type="none">
{udp, Socket, IP, InPortNo, Packet}</code>
        <p>Note that arriving UDP packets that are longer than
          the receive buffer option specifies, might be truncated
          without warning.</p>
        <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>

