php-doc-en/reference/sockets/functions/socket-create-pair.xml

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<!-- splitted from ./en/functions/sockets.xml, last change in rev 1.27 -->
  <refentry id="function.socket-create-pair">
   <refnamediv>
    <refname>socket_create_pair</refname>
    <refpurpose>Creates a pair of indistinguishable sockets and stores them in an array. </refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>bool</type><methodname>socket_create_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>
      <methodparam><type>array</type><parameter>&amp;fd</parameter></methodparam>
     </methodsynopsis>
     &warn.experimental.func;
    <para>
	 <function>socket_create_pair</function> creates two connected and indistinguishable sockets, and stores
	 them in <parameter>&amp;fd</parameter>. This function is commonly used in IPC (InterProcess Communication).
    </para>
    <para>
     The <parameter>domain</parameter> parameter specifies the protocol
     family to be used by the socket.
    </para>
    <table>
    <title>Available address/protocol families</title>
    <tgroup cols="2">
     <thead>
      <row>
       <entry>Domain</entry>
       <entry>Description</entry>
      </row>
     </thead>
     <tbody>
      <row>
       <entry>AF_INET</entry>
       <entry>
        IPv4 Internet based protocols. TCP and UDP are common protocols of
        this protocol family. Supported only in windows.
       </entry>
      </row>
      <row>
       <entry>AF_INET6</entry>
       <entry>
        IPv6 Internet based protocols. TCP and UDP are common protocols of
        this protocol family. Support added in <literal>PHP 5.0.0</literal>.
        Supported only in windows.
       </entry>
      </row>
      <row>
       <entry>AF_UNIX</entry>
       <entry>
        Local communication protocol family. High efficiency and low
        overhead make it a great form of IPC (Interprocess Communication).
       </entry>
      </row>
     </tbody>
    </tgroup>
    </table>
    <para>
     The <parameter>type</parameter> parameter selects the type of communication
     to be used by the socket.
    </para>
    <table>
    <title>Available socket types</title>
    <tgroup cols="2">
     <thead>
      <row>
       <entry>Type</entry>
       <entry>Description</entry>
      </row>
     </thead>
     <tbody>
      <row>
       <entry>SOCK_STREAM</entry>
       <entry>
         Provides sequenced, reliable, full-duplex, connection-based byte streams.
         An out-of-band data transmission mechanism may be supported.
         The TCP protocol is based on this socket type.
       </entry>
      </row>
      <row>
       <entry>SOCK_DGRAM</entry>
       <entry>
         Supports datagrams (connectionless, unreliable messages of a fixed maximum length).
         The UDP protocol is based on this socket type.
       </entry>
      </row>
        <row>
       <entry>SOCK_SEQPACKET</entry>
       <entry>
         Provides a sequenced, reliable, two-way connection-based data transmission path for
         datagrams of fixed maximum length;  a consumer is required to read an
         entire packet with each read call.
       </entry>
      </row>
      <row>
       <entry>SOCK_RAW</entry>
       <entry>
         Provides raw network protocol access. This special type of socket
         can be used to manually construct any type of protocol. A common use
         for this socket type is to perform ICMP requests (like ping,
         traceroute, etc).
       </entry>
      </row>
      <row>
       <entry>SOCK_RDM</entry>
       <entry>
         Provides a reliable datagram layer that does not guarantee ordering.
         This is most likely not implemented on your operating system.
       </entry>
      </row>
     </tbody>
    </tgroup>
    </table>
    <para>
     The <parameter>protocol</parameter> parameter sets the specific
     protocol within the specified <parameter>domain</parameter> to be used
     when communicating on the returned socket. The proper value can be retrieved by
     name by using <function>getprotobyname</function>. If
     the desired protocol is TCP, or UDP the corresponding constants
     <constant>SOL_TCP</constant>, and <constant>SOL_UDP</constant>
     can also be used.
    </para>
    <table>
    <title>Common protocols</title>
    <tgroup cols="2">
     <thead>
      <row>
       <entry>Name</entry>
       <entry>Description</entry>
      </row>
     </thead>
     <tbody>
      <row>
       <entry>icmp</entry>
       <entry>
        The Internet Control Message Protocol is used primarily by gateways
        and hosts to report errors in datagram communication. The "ping"
        command (present in most modern operating systems) is an example
        application of ICMP.
       </entry>
      </row>
      <row>
       <entry>udp</entry>
       <entry>
        The User Datagram Protocol is a connectionless, unreliable,
        protocol with fixed record lengths. Due to these aspects, UDP
        requires a minimum amount of protocol overhead.
       </entry>
      </row>
        <row>
       <entry>tcp</entry>
       <entry>
        The Transmission Control Protocol is a reliable, connection based,
        stream oriented, full duplex protocol. TCP guarantees that all data packets
        will be received in the order in which they were sent. If any packet is somehow
        lost during communication, TCP will automatically retransmit the packet until
        the destination host acknowledges that packet. For reliability and performance
        reasons, the TCP implementation itself decides the appropriate octet boundaries
        of the underlying datagram communication layer. Therefore, TCP applications must
        allow for the possibility of partial record transmission.
       </entry>
      </row>
     </tbody>
    </tgroup>
    </table>
	<para>
    <example>
    <title><function>socket_create_pair</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
$sockets = array();
$uniqid = uniqid('');
if (file_exists("/tmp/$uniqid.sock")) {
	die('Temporary socket already exists.');
}
/* Setup socket pair */
if (!socket_create_pair(AF_UNIX, SOCK_STREAM, 0, $sockets)) {
    echo socket_strerror(socket_last_error());
}
/* Send and Recieve Data */
if (!socket_write($sockets[0], "ABCdef123\n", strlen("ABCdef123\n"))) {
    echo socket_strerror(socket_last_error());
}
if (!$data = socket_read($sockets[1], strlen("ABCdef123\n"), PHP_BINARY_READ)) {
    echo socket_strerror(socket_last_error());
}
var_dump($data);

/* Close sockets */
socket_close($sockets[0]);
socket_close($sockets[1]);
?>
]]>
    </programlisting>
    </example>
    </para>
    <para>
    <example>
    <title><function>socket_create_pair</function> IPC example</title>
    <programlisting role="php">
<![CDATA[
<?php
$ary = array();
$strone = 'Message From Parent.';
$strtwo = 'Message From Child.';
if (!socket_create_pair(AF_UNIX, SOCK_STREAM, 0, $ary)) {
    echo socket_strerror(socket_last_error());
}
$pid = pcntl_fork();
if ($pid == -1) {
    echo 'Could not fork Process.';
} elseif ($pid) {
    /*parent*/
    socket_close($ary[0]);
    if (!socket_write($ary[1], $strone, strlen($strone))) {
    	echo socket_strerror(socket_last_error());
    }
    if (socket_read($ary[1], strlen($strtwo), PHP_BINARY_READ) == $strtwo) {
        echo "Recieved $strtwo\n";
    }
	socket_close($ary[1]);
} else {
    /*child*/
    socket_close($ary[1]);
    if (!socket_write($ary[0], $strtwo, strlen($strtwo))) {
        echo socket_strerror(socket_last_error());
    }
    if (socket_read($ary[0], strlen($strone), PHP_BINARY_READ) == $strone) {
        echo "Recieved $strone\n";
    }
	socket_close($ary[0]);
}
?>
]]>
    </programlisting>
    </example>
    </para>
   </refsect1>
  </refentry>

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