使用PHP创建一个socket服务端

　　与常规web开发不同，使用socket开发可以摆脱http的限制。可自定义协议，使用长连接、PHP代码常驻内存等。学习资料来源于workerman官方视频与文档.

　　通常创建一个socket服务包括这几个简单的步骤：

　　　　1.创建一个socket套接字，监听在某协议的某个端口，如：tcp的9865端口，为了是外网可以访问，地址为0.0.0.0，监听地址应为这种格式tcp://0.0.0.0:9865

　　　　2.将监听socket设置为非阻塞，若不设置，程序会在客户端连接没有发消息时阻塞。

　　　　3.程序阻塞在I/0复用函数stream_select，一旦有读取到的新事件则进行处理。

　　　　4.处理客户端发送的数据。若读取的socket连接为监听socket表示有新的连接，否则为当前连接发送了数据。若读取到空或返回了false，则表示客户端断开。

　　一个简单的demo：

<?php
 
    class Worker{
        //监听socket
        protected $socket = NULL;
 
        //所有的socket连接
        protected $allSockets = array();
 
        //连接事件回调
        public $onConnect = NULL;
 
        //断线事件回调
        public $onClose = NULL;
 
        //接收消息事件回调
        public $onMessage = NULL;
 
        public function __construct($socket_address) {
            //创建一个socket监听
            $this->socket = stream_socket_server($socket_address);
 
            //设置为非阻塞
            stream_set_blocking($this->socket, 0);
 
            //将socket监听加入allSockets
            $this->allSockets[(int)$this->socket] = $this->socket; 
        }
 
        public function run() {
            while(true) {
                //不监听可写事件与带外数据事件
                $write = $except = array();
                //监听所有的socket事件
                $read = $this->allSockets;
                //整个进程阻塞在这里，持续监听可读事件
                //此处参数均为引用传递，在函数中会改变传值
                stream_select($read, $write, $except, 60);
 
                //处理所有可读事件
                foreach ($read as $index => $socket) {
                    //如果是监听socket，此处表示有新的连接
                    if ($socket === $this->socket) {
                        //通过stream_socket_accept获取新的连接
                        $new_conn_socket = stream_socket_accept($socket);
 
                        if ($this->onConnect) {
                            //触发连接事件的回调,并将当前连接传递给回掉函数
                            call_user_func($this->onConnect, $socket);
                        }
                        //记录此socket连接,以便于sream_select监听可读事件
                        $this->allSockets[(int)$new_conn_socket] = $new_conn_socket;
                    } else
                    //如果可读事件不为监听socket，则表示对应客户端有数据发过来
                    {
                        //从连接中读取数据
                        $buffer = fread($socket, 65535);
                        //如果数据为空，表示客户端已经断开连接
                        if ('' === $buffer || false === $buffer) {
                            //尝试触发onClose回调
                            if ($this->onClose) {
                                call_user_func($this->onClose, $socket);
                            }
                            fclose($socket);
                            //关闭socket连接并从allSockets中删除
                            unset($this->allSockets[(int)$socket]);
                            continue;
                        }
                        //表示一个正常的连接，已经读取到消息，交给回掉函数处理
                        if ($this->onMessage) {
                            call_user_func($this->onMessage, $socket, $buffer);
                        }
                    }
                }
            }
        }
    }
 
    $worker = new Worker('tcp://0.0.0.0:9865');
 
    $worker->onConnect = function ($conn) {
        echo '新的连接来了';
    };
    $worker->onClose = function ($conn) {
        echo '连接断开了';
    };
    $worker->onMessage = function ($conn, $message) {
        $http_resonse = "HTTP/1.1 200 OK\r\n";
        $http_resonse .= "Connection: keep-alive\r\n";
        $http_resonse .= "Server: php socket server\r\n";
        $http_resonse .= "Content-length: 11\r\n\r\n";
        $http_resonse .= "hello world";
        fwrite($conn, $http_resonse);
    };
 
    $worker->run();