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Last updated: Tue, 19 Sep 2006

CXLVI. Socket Functions


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.

For a more generic client-side socket interface, see stream_socket_client(), stream_socket_server(), fsockopen(), and pfsockopen().

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.

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 Unix Socket FAQ might be a good start.


No external libraries are needed to build this extension.


The socket functions described here are part of an extension to PHP which must be enabled at compile time by giving the --enable-sockets option to configure.

Note: IPv6 Support was added with PHP 5.0.0.

Runtime Configuration

This extension has no configuration directives defined in php.ini.

Resource Types

This extension has no resource types defined.

Predefined Constants

The constants below are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.

AF_UNIX (integer)

AF_INET (integer)

AF_INET6 (integer)

SOCK_STREAM (integer)

SOCK_DGRAM (integer)

SOCK_RAW (integer)


SOCK_RDM (integer)

MSG_OOB (integer)

MSG_WAITALL (integer)

MSG_PEEK (integer)


SO_DEBUG (integer)

SO_REUSEADDR (integer)

SO_KEEPALIVE (integer)

SO_DONTROUTE (integer)

SO_LINGER (integer)

SO_BROADCAST (integer)

SO_OOBINLINE (integer)

SO_SNDBUF (integer)

SO_RCVBUF (integer)

SO_SNDLOWAT (integer)

SO_RCVLOWAT (integer)

SO_SNDTIMEO (integer)

SO_RCVTIMEO (integer)

SO_TYPE (integer)

SO_ERROR (integer)

SOL_SOCKET (integer)



SOL_TCP (integer)

SOL_UDP (integer)

Socket Errors

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 E_WARNING message describing the error. Sometimes this doesn't happen to the desire of the developer. For example the function socket_read() may suddenly emit an E_WARNING message because the connection broke unexpectedly. It's common to suppress the warning with the @-operator and catch the error code within the application with the socket_last_error() function. You may call the socket_strerror() function with this error code to retrieve a string describing the error. See their description for more information.

Note: The E_WARNING messages generated by the socket extension are in English though the retrieved error message will appear depending on the current locale (LC_MESSAGES):

Warning - socket_bind() unable to bind address [98]: Die Adresse wird bereits verwendet


Example 1. Socket example: Simple TCP/IP server

This example shows a simple talkback server. Change the address and port variables to suit your setup and execute. You may then connect to the server with a command similar to: telnet 10000 (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'.

#!/usr/local/bin/php -q

/* Allow the script to hang around waiting for connections. */

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

$address = '';
$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";
    /* 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($buf)) {
        if ($buf == 'quit') {
        if ($buf == 'shutdown') {
            break 2;
        $talkback = "PHP: You said '$buf'.\n";
        socket_write($msgsock, $talkback, strlen($talkback));
        echo "$buf\n";
    } while (true);
} while (true);


Example 2. Socket example: Simple TCP/IP client

This example shows a simple, one-shot HTTP client. It simply connects to a page, submits a HEAD request, echoes the reply, and exits.


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...";
echo "OK.\n\n";

Table of Contents
socket_accept -- Accepts a connection on a socket
socket_bind -- Binds a name to a socket
socket_clear_error -- Clears the error on the socket or the last error code
socket_close -- Closes a socket resource
socket_connect -- Initiates a connection on a socket
socket_create_listen -- Opens a socket on port to accept connections
socket_create_pair -- Creates a pair of indistinguishable sockets and stores them in an array
socket_create -- Create a socket (endpoint for communication)
socket_get_option -- Gets socket options for the socket
socket_getpeername --  Queries the remote side of the given socket which may either result in host/port or in a Unix filesystem path, dependent on its type
socket_getsockname --  Queries the local side of the given socket which may either result in host/port or in a Unix filesystem path, dependent on its type
socket_last_error -- Returns the last error on the socket
socket_listen -- Listens for a connection on a socket
socket_read -- Reads a maximum of length bytes from a socket
socket_recv -- Receives data from a connected socket
socket_recvfrom -- Receives data from a socket, connected or not
socket_select --  Runs the select() system call on the given arrays of sockets with a specified timeout
socket_send -- Sends data to a connected socket
socket_sendto -- Sends a message to a socket, whether it is connected or not
socket_set_block --  Sets blocking mode on a socket resource
socket_set_nonblock -- Sets nonblocking mode for file descriptor fd
socket_set_option -- Sets socket options for the socket
socket_shutdown -- Shuts down a socket for receiving, sending, or both
socket_strerror -- Return a string describing a socket error
socket_write -- Write to a socket

Last updated: Tue, 19 Sep 2006