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<refentry xml:id="function.stream-socket-pair" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>stream_socket_pair</refname>
  <refpurpose>
   Creates a pair of connected, indistinguishable socket streams
  </refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type class="union"><type>array</type><type>false</type></type><methodname>stream_socket_pair</methodname>
   <methodparam><type>int</type><parameter>domain</parameter></methodparam>
   <methodparam><type>int</type><parameter>type</parameter></methodparam>
   <methodparam><type>int</type><parameter>protocol</parameter></methodparam>
  </methodsynopsis>
  <para>
   <function>stream_socket_pair</function> creates a pair of connected,
   indistinguishable socket streams. This function is commonly used in IPC
   (Inter-Process Communication).     
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>domain</parameter></term>
     <listitem>
      <para>
       The protocol family to be used: <constant>STREAM_PF_INET</constant>,
       <constant>STREAM_PF_INET6</constant> or
       <constant>STREAM_PF_UNIX</constant>
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>type</parameter></term>
     <listitem>
      <para>
       The type of communication to be used:
       <constant>STREAM_SOCK_DGRAM</constant>,
       <constant>STREAM_SOCK_RAW</constant>,
       <constant>STREAM_SOCK_RDM</constant>,
       <constant>STREAM_SOCK_SEQPACKET</constant> or
       <constant>STREAM_SOCK_STREAM</constant>
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>protocol</parameter></term>
     <listitem>
      <para>
       The protocol to be used: <constant>STREAM_IPPROTO_ICMP</constant>,
       <constant>STREAM_IPPROTO_IP</constant>,
       <constant>STREAM_IPPROTO_RAW</constant>,
       <constant>STREAM_IPPROTO_TCP</constant> or
       <constant>STREAM_IPPROTO_UDP</constant>       
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
  <note>
   <simpara>
    Please consult the <link linkend="stream.constants">Streams constant
     list</link> for further details on each constant.
   </simpara>
  </note>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns an <type>array</type> with the two socket resources on success, or
   &false; on failure.
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title>A <function>stream_socket_pair</function> example</title>
    <para>
     This example shows the basic usage of
     <function>stream_socket_pair</function> in Inter-Process Communication.
    </para>
    <programlisting role="php">
<![CDATA[
<?php

$sockets = stream_socket_pair(STREAM_PF_UNIX, STREAM_SOCK_STREAM, STREAM_IPPROTO_IP);
$pid     = pcntl_fork();

if ($pid == -1) {
     die('could not fork');

} else if ($pid) {
     /* parent */
    fclose($sockets[0]);

    fwrite($sockets[1], "child PID: $pid\n");
    echo fgets($sockets[1]);

    fclose($sockets[1]);

} else {
    /* child */
    fclose($sockets[1]);

    fwrite($sockets[0], "message from child\n");
    echo fgets($sockets[0]);

    fclose($sockets[0]);
}

?>
]]>
    </programlisting>
    &example.outputs.similar;
    <screen>
<![CDATA[
child PID: 1378
message from child
]]>
    </screen>
   </example>
  </para>
 </refsect1>

</refentry>
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