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 <reference id="ref.sockets">
  <title>Socket Functions</title>
  <titleabbrev>Sockets</titleabbrev>

  <partintro>

   <section id="sockets.intro">
    &reftitle.intro;
    <para>
     The socket extension implements a low-level interface to the socket
     communication functions based on the popular BSD sockets, providing the
     possibility to act as a socket server as well as a client.
    </para>
    <para>
     For a more generic client-side socket interface, see
     <function>stream_socket_client</function>, 
     <function>stream_socket_server</function>,
     <function>fsockopen</function>, and
     <function>pfsockopen</function>.
    </para>
    <para>
     When using these functions, it is important to remember that while
     many of them have identical names to their C counterparts, they
     often have different declarations. Please be sure to read the
     descriptions to avoid confusion.
    </para>
    <para>
     Those unfamiliar with socket programming can find a lot
     of useful material in the appropriate Unix man pages, and there is a great
     deal of tutorial information on socket programming in C on the web, much
     of which can be applied, with slight modifications, to socket programming
     in PHP. The <ulink url="&url.socket.faq;">Unix Socket
     FAQ</ulink> might be a good start.
    </para>
   </section>
   
   <section id="sockets.requirements">
    &reftitle.required;
    &no.requirement;
   </section>
   
   &reference.sockets.configure;
   
   <section id="sockets.configuration">
    &reftitle.runtime;
    &no.config;
   </section>

   <section id="sockets.resources">
    &reftitle.resources;
    &no.resource;
   </section>

   &reference.sockets.constants;

   <section id="sockets.errors">
    <title>Socket Errors</title>
    <para>
     The socket extension was written to provide a usable interface to the
     powerful BSD sockets. Care has been taken that the functions work equally
     well on Win32 and Unix implementations. Almost all of the sockets
     functions may fail under certain conditions and therefore emit an
     <constant>E_WARNING</constant> message describing the error. Sometimes this
     doesn't happen to the desire of the developer. For example the function
     <function>socket_read</function> may suddenly emit an
     <constant>E_WARNING</constant> message because the connection broke
     unexpectedly. It's common to suppress the warning with the
     <literal>@</literal>-operator and catch the error code within the
     application with the <function>socket_last_error</function> function. You
     may call the <function>socket_strerror</function> function with this error
     code to retrieve a string describing the error. See their description for
     more information.
    </para>
    <note>
     <para>
      The <constant>E_WARNING</constant> messages generated by the socket
      extension are in English though the retrieved error message will appear
      depending on the current locale (<constant>LC_MESSAGES</constant>):
      <programlisting role="php">
<![CDATA[
Warning - socket_bind() unable to bind address [98]: Die Adresse wird bereits verwendet
]]>
      </programlisting>
     </para>
    </note>
   </section>
   
   <section id="sockets.examples">
    &reftitle.examples;
    <para>
     <example>
      <title>Socket example: Simple TCP/IP server</title>
      <para>
       This example shows a simple talkback server. Change the
       <varname>address</varname> and <varname>port</varname> variables
       to suit your setup and execute. You may then connect to the
       server with a command similar to: <command>telnet 192.168.1.53
       10000</command> (where the address and port match your
       setup). Anything you type will then be output on the server
       side, and echoed back to you. To disconnect, enter 'quit'.
      </para>
      <programlisting role="php">
<![CDATA[
#!/usr/local/bin/php -q
<?php
error_reporting(E_ALL);

/* Allow the script to hang around waiting for connections. */
set_time_limit(0);

/* Turn on implicit output flushing so we see what we're getting
 * as it comes in. */
ob_implicit_flush();

$address = '192.168.1.53';
$port = 10000;

if (($sock = socket_create(AF_INET, SOCK_STREAM, SOL_TCP)) < 0) {
    echo "socket_create() failed: reason: " . socket_strerror($sock) . "\n";
}

if (($ret = socket_bind($sock, $address, $port)) < 0) {
    echo "socket_bind() failed: reason: " . socket_strerror($ret) . "\n";
}

if (($ret = socket_listen($sock, 5)) < 0) {
    echo "socket_listen() failed: reason: " . socket_strerror($ret) . "\n";
}

do {
    if (($msgsock = socket_accept($sock)) < 0) {
        echo "socket_accept() failed: reason: " . socket_strerror($msgsock) . "\n";
        break;
    }
    /* Send instructions. */
    $msg = "\nWelcome to the PHP Test Server. \n" .
        "To quit, type 'quit'. To shut down the server type 'shutdown'.\n";
    socket_write($msgsock, $msg, strlen($msg));

    do {
        if (false === ($buf = socket_read($msgsock, 2048, PHP_NORMAL_READ))) {
            echo "socket_read() failed: reason: " . socket_strerror($ret) . "\n";
            break 2;
        }
        if (!$buf = trim($buf)) {
            continue;
        }
        if ($buf == 'quit') {
            break;
        }
        if ($buf == 'shutdown') {
            socket_close($msgsock);
            break 2;
        }
        $talkback = "PHP: You said '$buf'.\n";
        socket_write($msgsock, $talkback, strlen($talkback));
        echo "$buf\n";
    } while (true);
    socket_close($msgsock);
} while (true);

socket_close($sock);
?>
]]>
      </programlisting>
     </example>
    </para>
    <para>
     <example>
      <title>Socket example: Simple TCP/IP client</title>
      <para>
       This example shows a simple, one-shot HTTP client. It simply
       connects to a page, submits a HEAD request, echoes the reply,
       and exits.
      </para>
      <programlisting role="php">
<![CDATA[
<?php
error_reporting(E_ALL);

echo "<h2>TCP/IP Connection</h2>\n";

/* Get the port for the WWW service. */
$service_port = getservbyname('www', 'tcp');

/* Get the IP address for the target host. */
$address = gethostbyname('www.example.com');

/* Create a TCP/IP socket. */
$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
if ($socket < 0) {
    echo "socket_create() failed: reason: " . socket_strerror($socket) . "\n";
} else {
    echo "OK.\n";
}

echo "Attempting to connect to '$address' on port '$service_port'...";
$result = socket_connect($socket, $address, $service_port);
if ($result < 0) {
    echo "socket_connect() failed.\nReason: ($result) " . socket_strerror($result) . "\n";
} else {
    echo "OK.\n";
}

$in = "HEAD / HTTP/1.1\r\n";
$in .= "Host: www.example.com\r\n";
$in .= "Connection: Close\r\n\r\n";
$out = '';

echo "Sending HTTP HEAD request...";
socket_write($socket, $in, strlen($in));
echo "OK.\n";

echo "Reading response:\n\n";
while ($out = socket_read($socket, 2048)) {
    echo $out;
}

echo "Closing socket...";
socket_close($socket);
echo "OK.\n\n";
?>
]]>
      </programlisting>
     </example>
    </para>
   </section>
  </partintro>

&reference.sockets.functions;

 </reference>
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