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

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<refentry xmlns="http://docbook.org/ns/docbook" xml: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 role="description">
  &reftitle.description;
  <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 role="reference">fd</parameter></methodparam>
  </methodsynopsis>
  <para>
   <function>socket_create_pair</function> creates two connected and
   indistinguishable sockets, and stores them in <parameter>fd</parameter>.
   This function is commonly used in IPC (InterProcess Communication).
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>domain</parameter></term>
     <listitem>
      <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 PHP 5.0.0.
           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>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>type</parameter></term>
     <listitem>
      <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>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>protocol</parameter></term>
     <listitem>
      <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>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>fd</parameter></term>
     <listitem>
      <para>
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   &return.success;
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>socket_create_pair</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
$sockets = array();
/* Setup socket pair */
if (socket_create_pair(AF_UNIX, SOCK_STREAM, 0, $sockets) === false) {
    echo "socket_create_pair failed. Reason: ".socket_strerror(socket_last_error());
}
/* Send and Recieve Data */
if (socket_write($sockets[0], "ABCdef123\n", strlen("ABCdef123\n")) === false) {
    echo "socket_write() failed. Reason: ".socket_strerror(socket_last_error($sockets[0]));
}
if (($data = socket_read($sockets[1], strlen("ABCdef123\n"), PHP_BINARY_READ) === false) {
    echo "socket_read() failed. Reason: ".socket_strerror(socket_last_error($sockets[1]));
}
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) === false) {
    echo "socket_create_pair() failed. Reason: ".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)) === false) {
        echo "socket_write() failed. Reason: ".socket_strerror(socket_last_error($ary[1]));
    }
    if (socket_read($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)) === false) {
        echo "socket_write() failed. Reason: ".socket_strerror(socket_last_error($ary[0]));
    }
    if (socket_read($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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