解析:通过php socket并借助telnet实现简单的聊天程序

#!/usr/bin/env php
<?php
//author:zhxia
if(!extension_loaded('sockets')){
    die('the sockets extension is not loaded!');
}
const PORT=9981;
$socket=socket_create(AF_INET,SOCK_STREAM,SOL_TCP) or die('socket create error!');
#通过设置这个选项，进行端口的重用
socket_set_option($socket,SOL_SOCKET,SO_REUSEADDR,1);
socket_bind($socket,0,PORT);
socket_listen($socket);
#使用非阻塞模式
socket_set_nonblock($socket);
echo 'listen on port '.PORT.'...'.PHP_EOL;
$clients=array($socket);
while(TRUE){
    $read=$clients;
    $write=$except=array();
    //通过select系统调用，检测socket的状态是否改变
    if(socket_select($read,$write,$except,0)<1){
        continue;
    }
    //检测是否有客户端来进行连接
    if(in_array($socket,$read)){
        $clients[]=$newsocket=socket_accept($socket);
        socket_write($newsocket,"welcome!\nthere are ".(count($clients)-1)." client here\n");
        socket_getpeername($newsocket,$ip);
        echo "new client connected:$ip\n";
        $key=array_search($newsocket,$read);
        unset($read[$key]);
    }

    foreach($read as $read_socket){
        $data=@socket_read($read_socket,1024,PHP_NORMAL_READ);
        if($data===false){
            //如果没有取到数据，说明该客户端已经断开
            $key=array_search($read_socket,$clients);
            unset($clients[$key]);
            echo "client disconnectd.\n";
            continue;
        }
        $data=trim($data);
        if(!empty($data)){
            foreach($clients as $write_socket){
                //排除服务器端和自身,然后将数据发送给所有的其他客户端
                if($write_socket==$socket||$write_socket==$read_socket){
                    continue;
                }
                socket_write($write_socket,"$data\n");
            }
        }
    }
}
socket_close($socket);