PHP: socket_accept - Manual (original) (raw)

(PHP 4 >= 4.1.0, PHP 5, PHP 7, PHP 8)

socket_accept — Accepts a connection on a socket

Description

The Socket instance returned bysocket_accept() may not be used to accept new connections. The original listening socketsocket, however, remains open and may be reused.

Return Values

Returns a new Socket instance on success, or [false](reserved.constants.php#constant.false) on error. The actual error code can be retrieved by callingsocket_last_error(). This error code may be passed tosocket_strerror() to get a textual explanation of the error.

Changelog

Version Description
8.0.0 On success, this function returns a Socket instance now; previously, a resource was returned.

See Also

Found A Problem?

lars at opdenkamp dot eu

17 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( <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>u</mi><mi>i</mi><mi>d</mi><mo separator="true">,</mo></mrow><annotation encoding="application/x-tex">uid, </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8889em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">u</span><span class="mord mathnormal">i</span><span class="mord mathnormal">d</span><span class="mpunct">,</span></span></span></span>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, <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>a</mi><mi>d</mi><mi>d</mi><mi>r</mi><mi>e</mi><mi>s</mi><mi>s</mi><mo separator="true">,</mo></mrow><annotation encoding="application/x-tex">address, </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8889em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">a</span><span class="mord mathnormal">dd</span><span class="mord mathnormal">ress</span><span class="mpunct">,</span></span></span></span>port)) < 0)
    {
        echo "failed to bind socket: ".socket_strerror($ret)."\n";
        exit();
    }

    if( ( <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>r</mi><mi>e</mi><mi>t</mi><mo>=</mo><mi>s</mi><mi>o</mi><mi>c</mi><mi>k</mi><mi>e</mi><msub><mi>t</mi><mi>l</mi></msub><mi>i</mi><mi>s</mi><mi>t</mi><mi>e</mi><mi>n</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">ret = socket_listen( </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6151em;"></span><span class="mord mathnormal">re</span><span class="mord mathnormal">t</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">soc</span><span class="mord mathnormal" style="margin-right:0.03148em;">k</span><span class="mord mathnormal">e</span><span class="mord"><span class="mord mathnormal">t</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.3361em;"><span style="top:-2.55em;margin-left:0em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight" style="margin-right:0.01968em;">l</span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span><span class="mord mathnormal">i</span><span class="mord mathnormal">s</span><span class="mord mathnormal">t</span><span class="mord mathnormal">e</span><span class="mord mathnormal">n</span><span class="mopen">(</span></span></span></span>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)
    {
        <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>c</mi><mi>o</mi><mi>n</mi><mi>n</mi><mi>e</mi><mi>c</mi><mi>t</mi><mi>i</mi><mi>o</mi><mi>n</mi><mo>=</mo><mi mathvariant="normal">@</mi><mi>s</mi><mi>o</mi><mi>c</mi><mi>k</mi><mi>e</mi><msub><mi>t</mi><mi>a</mi></msub><mi>c</mi><mi>c</mi><mi>e</mi><mi>p</mi><mi>t</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">connection = @socket_accept(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6595em;"></span><span class="mord mathnormal">co</span><span class="mord mathnormal">nn</span><span class="mord mathnormal">ec</span><span class="mord mathnormal">t</span><span class="mord mathnormal">i</span><span class="mord mathnormal">o</span><span class="mord mathnormal">n</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord">@</span><span class="mord mathnormal">soc</span><span class="mord mathnormal" style="margin-right:0.03148em;">k</span><span class="mord mathnormal">e</span><span class="mord"><span class="mord mathnormal">t</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.1514em;"><span style="top:-2.55em;margin-left:0em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight">a</span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span><span class="mord mathnormal">cce</span><span class="mord mathnormal">pt</span><span class="mopen">(</span></span></span></span>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

17 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";
        <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>c</mi><mi>l</mi><mi>i</mi><mi>e</mi><mi>n</mi><mi>t</mi><mi>s</mi><mo stretchy="false">[</mo><mo stretchy="false">]</mo><mo>=</mo></mrow><annotation encoding="application/x-tex">clients[] = </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">c</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal">i</span><span class="mord mathnormal">e</span><span class="mord mathnormal">n</span><span class="mord mathnormal">t</span><span class="mord mathnormal">s</span><span class="mopen">[</span><span class="mclose">]</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span></span></span></span>newc;
    }
}

?>

Greg MacLellan

22 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.

renmengyang567 at gmail dot com

6 years ago

<explain>
 This case is a very simple interaction between the TCP client side and the TCP server side

<?php
// create for simple-tcp-server
$sock = socket_create(AF_INET, SOCK_STREAM, getprotobyname('tcp'));
socket_bind($sock, '127.0.0.1',5000);
socket_listen($sock,1); <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>c</mi><mi>l</mi><mi>n</mi><msub><mi>t</mi><mi>s</mi></msub><mi>o</mi><mi>c</mi><mi>k</mi><mo>=</mo><mi>s</mi><mi>o</mi><mi>c</mi><mi>k</mi><mi>e</mi><msub><mi>t</mi><mi>a</mi></msub><mi>c</mi><mi>c</mi><mi>e</mi><mi>p</mi><mi>t</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">clnt_sock = socket_accept(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8444em;vertical-align:-0.15em;"></span><span class="mord mathnormal">c</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal">n</span><span class="mord"><span class="mord mathnormal">t</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.1514em;"><span style="top:-2.55em;margin-left:0em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight">s</span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span><span class="mord mathnormal">oc</span><span class="mord mathnormal" style="margin-right:0.03148em;">k</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">soc</span><span class="mord mathnormal" style="margin-right:0.03148em;">k</span><span class="mord mathnormal">e</span><span class="mord"><span class="mord mathnormal">t</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.1514em;"><span style="top:-2.55em;margin-left:0em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight">a</span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span><span class="mord mathnormal">cce</span><span class="mord mathnormal">pt</span><span class="mopen">(</span></span></span></span>sock); //阻塞
$st = "hello world ^_^";
socket_write($clnt_sock, <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>s</mi><mi>t</mi><mo separator="true">,</mo><mi>s</mi><mi>t</mi><mi>r</mi><mi>l</mi><mi>e</mi><mi>n</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">st,strlen(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">s</span><span class="mord mathnormal">t</span><span class="mpunct">,</span><span class="mspace" style="margin-right:0.1667em;"></span><span class="mord mathnormal">s</span><span class="mord mathnormal">t</span><span class="mord mathnormal" style="margin-right:0.02778em;">r</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal">e</span><span class="mord mathnormal">n</span><span class="mopen">(</span></span></span></span>st));
socket_close($clnt_sock);
socket_close($sock);
?>

<?php
//create for simple-tcp-client     
$clnt_sock = socket_create(AF_INET, SOCK_STREAM, getprotobyname('tcp'));
socket_connect($clnt_sock, '127.0.0.1', 5000); <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>r</mi><mi>e</mi><mi>t</mi><mo>=</mo><mi>s</mi><mi>o</mi><mi>c</mi><mi>k</mi><mi>e</mi><msub><mi>t</mi><mi>r</mi></msub><mi>e</mi><mi>a</mi><mi>d</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">ret= socket_read(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6151em;"></span><span class="mord mathnormal">re</span><span class="mord mathnormal">t</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">soc</span><span class="mord mathnormal" style="margin-right:0.03148em;">k</span><span class="mord mathnormal">e</span><span class="mord"><span class="mord mathnormal">t</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.1514em;"><span style="top:-2.55em;margin-left:0em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight" style="margin-right:0.02778em;">r</span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span><span class="mord mathnormal">e</span><span class="mord mathnormal">a</span><span class="mord mathnormal">d</span><span class="mopen">(</span></span></span></span>clnt_sock, 1024);
print "from simple-tcp-server:".$ret.PHP_EOL;
socket_close($clnt_sock);
?>

<fruit>
from simple-tcp-server:hello world ^_^

gmkarl at gmail dot com

18 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.