# Socket Functions

## Introduction

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.

> Note: This extension has been moved to the » PECL repository and is no longer bundled with PHP as of PHP 5.3.0.

## Requirements

No external libraries are needed to build this extension.

## Installation

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

socket_accept(), socket_create_listen() and socket_create() return socket recources.

## 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_SEQPACKET` (integer)
`SOCK_RDM` (integer)
`MSG_OOB` (integer)
`MSG_WAITALL` (integer)
`MSG_PEEK` (integer)
`MSG_DONTROUTE` (integer)
`MSG_EOR` (integer)
`MSG_EOF` (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)
`PHP_NORMAL_READ` (integer)
`PHP_BINARY_READ` (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`

## Examples

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 192.168.1.53 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
<?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)) === false) {
echo "socket_create() failed: reason: " . socket_strerror(socket_last_error()) . "\n";
}
if (socket_bind($sock, $address, $port) === false) {
echo "socket_bind() failed: reason: " . socket_strerror(socket_last_error($sock)) . "\n";
}
if (socket_listen($sock, 5) === false) {
echo "socket_listen() failed: reason: " . socket_strerror(socket_last_error($sock)) . "\n";
}
do {
if (($msgsock = socket_accept($sock)) === false) {
echo "socket_accept() failed: reason: " . socket_strerror(socket_last_error($sock)) . "\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(socket_last_error($msgsock)) . "\n";
break 2;
}
if (!$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);
?>`

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.

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

## 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 whether or not it is connection-oriented
- 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