PHP 7.0.6 Released

    socket_accept

    (PHP 4 >= 4.1.0, PHP 5, PHP 7)

    socket_accept — Accepts a connection on a socket

    Description

    resource socket_accept ( resource $socket )

    After the socket socket has been created using socket_create(), bound to a name with socket_bind(), and told to listen for connections with socket_listen(), this function will accept incoming connections on that socket. Once a successful connection is made, a new socket resource is returned, which may be used for communication. If there are multiple connections queued on the socket, the first will be used. If there are no pending connections, socket_accept() will block until a connection becomes present. If socket has been made non-blocking using socket_set_blocking() or socket_set_nonblock(), FALSE will be returned.

    The socket resource returned by socket_accept() may not be used to accept new connections. The original listening socket socket, however, remains open and may be reused.

    Parameters

    socket

    A valid socket resource created with socket_create().

    Return Values

    Returns a new socket resource on success, or FALSE on error. The actual error code can be retrieved by calling socket_last_error(). This error code may be passed to socket_strerror() to get a textual explanation of the error.

    See Also

    User Contributed Notes

    lars at opdenkamp dot eu
    8 years ago
    If you want to make a daemon process that forks on each client connection, you'll find out that there's a bug in PHP. The child processes send SIGCHLD to their parent when they exit but the parent can't handle signals while it's waiting for socket_accept (blocking).

    Here is a piece of code that makes a non-blocking forking server.

    #!/usr/bin/php -q
    <?php
    /**
      * Listens for requests and forks on each connection
      */

    $__server_listening = true;

    error_reporting(E_ALL);
    set_time_limit(0);
    ob_implicit_flush();
    declare(    ticks = 1);

    become_daemon();

    /* nobody/nogroup, change to your host's uid/gid of the non-priv user */
    change_identity(65534, 65534);

    /* handle signals */
    pcntl_signal(SIGTERM, 'sig_handler');
    pcntl_signal(SIGINT, 'sig_handler');
    pcntl_signal(SIGCHLD, 'sig_handler');

    /* change this to your own host / port */
    server_loop("127.0.0.1", 1234);

    /**
      * Change the identity to a non-priv user
      */
    function change_identity( $uid, $gid )
    {
        if( !    posix_setgid( $gid ) )
        {
            print     "Unable to setgid to " . $gid . "!\n";
            exit;
        }

        if( !    posix_setuid( $uid ) )
        {
            print     "Unable to setuid to " . $uid . "!\n";
            exit;
        }
    }

    /**
      * Creates a server socket and listens for incoming client connections
      * @param string $address The address to listen on
      * @param int $port The port to listen on
      */
    function server_loop($address, $port)
    {
        GLOBAL     $__server_listening;

        if((    $sock = socket_create(AF_INET, SOCK_STREAM, 0)) < 0)
        {
            echo     "failed to create socket: ".socket_strerror($sock)."\n";
            exit();
        }

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

        if( (     $ret = socket_listen( $sock, 0 ) ) < 0 )
        {
            echo     "failed to listen to socket: ".socket_strerror($ret)."\n";
            exit();
        }

            socket_set_nonblock($sock);
       
        echo     "waiting for clients to connect\n";

        while (    $__server_listening)
        {
                $connection = @socket_accept($sock);
            if (    $connection === false)
            {
                    usleep(100);
            }elseif (    $connection > 0)
            {
                    handle_client($sock, $connection);
            }else
            {
                echo     "error: ".socket_strerror($connection);
                die;
            }
        }
    }

    /**
      * Signal handler
      */
    function sig_handler($sig)
    {
        switch(    $sig)
        {
            case     SIGTERM:
            case     SIGINT:
                exit();
            break;

            case     SIGCHLD:
                    pcntl_waitpid(-1, $status);
            break;
        }
    }

    /**
      * Handle a new client connection
      */
    function handle_client($ssock, $csock)
    {
        GLOBAL     $__server_listening;

            $pid = pcntl_fork();

        if (    $pid == -1)
        {
                /* fork failed */
                echo "fork failure!\n";
            die;
        }elseif (    $pid == 0)
        {
                /* child process */
                $__server_listening = false;
                socket_close($ssock);
                interact($csock);
                socket_close($csock);
        }else
        {
                socket_close($csock);
        }
    }

    function     interact($socket)
    {
            /* TALK TO YOUR CLIENT */
    }

    /**
      * Become a daemon by forking and closing the parent
      */
    function become_daemon()
    {
            $pid = pcntl_fork();
       
        if (    $pid == -1)
        {
                /* fork failed */
                echo "fork failure!\n";
            exit();
        }elseif (    $pid)
        {
                /* close the parent */
                exit();
        }else
        {
                /* child becomes our daemon */
                posix_setsid();
                chdir('/');
                umask(0);
            return     posix_getpid();

        }
    }

    ?>
    Boylett
    8 years ago
    If you want to have multiple clients on a server you will have to use non blocking.

    <?php

    $clients     = array();
    $socket = socket_create(AF_INET,SOCK_STREAM,SOL_TCP);
    socket_bind($socket,'127.0.0.1',$port);
    socket_listen($socket);
    socket_set_nonblock($socket);

    while(    true)
    {
        if((    $newc = socket_accept($socket)) !== false)
        {
            echo     "Client $newc has connected\n";
                $clients[] = $newc;
        }
    }

    ?>
    gmkarl at gmail dot com
    8 years ago
    Be aware signal handler functions set with pcntl_signal are not called while a socket is blocking waiting for a connection; the signal is absorbed silently and the handler called when a connection is made.
    mightyplow at gmail dot com
    1 year ago
    In order to make many clients connectable to the server, you have to set the accepted socket also to non-blocking. Otherwise the accepted connection will block further incoming connections.

    while (true) {
        $newSock = @socket_accept($sock);

        if ($newSock) {
            echo 'client connected';

            socket_set_nonblock($newSock);
        }
    }
    Greg MacLellan
    12 years ago
    The socket returned by this resource will be non-blocking, regardless of what the listening socket is set to. This is actually true for all FCNTL modifiers.
    simon at 180solutions dot com
    10 years ago
    >Accepting a connection using php-sockets:
    >
    >$fd = socket_create(AF_INET, SOCK_STREAM, 6 /* OR >getprotobyname("TCP")*/);
    >
    >$PORT = 5000;
    >
    >socket_bind($fd, "0.0.0.0", $PORT);
    >
    >while(true)
    >{
    >$remote_fd = socket_accept($fd);
    >
    >remote_socket_client_handle($remote_fd);
    >
    >}
    >
    >It is simple!

    This example doesn't work. You have to call socket_listen($fd) after your bind in order to accept incoming connections.

    Simon
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