socket_accept()

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

接受一个Socket连接

说明

socket_accept(resource $socket):Socket|false

首先创建socket_create()，然后绑定socket_bind()，然后侦听连接socket_listen()。连接成功后，会返回一个新的Socket实例，可用于通信。如果套接字上有多个连接排队，将使用第一个连接。如果没有连接，socket_accept()将阻塞，直到出现连接。如果socket 使用socket_set_blocking()或 socket_set_nonblock()使非阻塞，返回FALSE。

返回的 Socket 实例不能用于接受新连接。但是，原始侦听 socket 保持打开状态并可重复使用。

参数

$socket

返回值

成功时，返回一个 socket 资源；失败时，返回FALSE。要读取错误代码，可以调用socket_last_error()。这个错误代码可以通过socket_strerror()读取文字的错误说明。

参见

• socket_connect()开启一个套接字连接
• socket_listen()监听一个套接字的连接
• socket_create()创建一个套接字（通讯节点）
• socket_bind()给套接字绑定名字
• socket_strerror()返回一个描述套接字错误的字符串

实例

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();
  }
}
?>

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;
  }
}
?>

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.

<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);
$clnt_sock = socket_accept($sock); //阻塞
$st = "hello world ^_^";
socket_write($clnt_sock, $st,strlen($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);
$ret= socket_read($clnt_sock, 1024);
print "from simple-tcp-server:".$ret.PHP_EOL;
socket_close($clnt_sock);
?>
<fruit>
from simple-tcp-server:hello world ^_^

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.

>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

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);
  }
}