<?php

$host = "127.0.0.1";

// 指定监听的端口，注意该端口不能与现有应用的端口冲突

$port = '9505';

$null = null;

// 创建Socket。AF_INET：代表通信时使用IPv4协议；SOCK_STREAM：代表传输的数据是二进制流数据；SOL_TCP：代表底层使用的协议是TCP

$socket = socket_create ( AF_INET, SOCK_STREAM, SOL_TCP );

// 指定Socket相应的属性。SOL_SOCKET：设定协议的等级；SO_REUSEADDR：设置端口释放之后可以立即被使用

socket_set_option ( $socket, SOL_SOCKET, SO_REUSEADDR, 1 );

// 绑定端口

socket_bind ( $socket, 0, $port );

// 监听端口

socket_listen ( $socket );

// 声明一个数组，用于存放所有的客户端连接

$clients = array (

        $socket

);

while ( true ) {

    $changed_socket = $clients;

    // 在当前数组中获取活跃的Socket连接，即当前正在发送请求的连接或正在传输数据的连接等

    socket_select ( $changed_socket, $null, $null, 0, 10 );

    // 判断当前的Socket是否为活跃的Socket，如果是，说明客户端在请求连接

    if (in_array ( $socket, $changed_socket )) {

        echo "client connecting";

        // 接受连接

        $socket_new = socket_accept ( $socket );

        $clients [] = $socket_new;

        // 发送握手信息

        $header = socket_read ( $socket_new, 1024 );

        perform_handshaking ( $header, $socket_new, $host, $port );

        // 在连接成功后，当前Socket要从活跃Socket列表中删除，否则会陷入死循环

        $key = array_search ( $socket, $changed_socket );

        unset ( $changed_socket [$key] );

    } else {

        // 不是新连接，是客户端在发送数据

        // 服务器开始读取客户端发送的数据

        foreach ( $changed_socket as $v ) {

            while ( socket_recv ( $v, $buf, 1024, 0 ) >= 1 ) {

                // 解包数据

                $received_text = unmask ( $buf );

                // 将数据解包后转成JSON对象

                $msgJson = json_decode ( $received_text );

                // 读取数据

                $namer = $msgJson->namer;

                $content = $msgJson->content;

                // 将数据进行编码

                $message = mask ( json_encode ( [

                        'namer' => $namer,

                        'content' => $content,

                        'type' => 'usermsg'

                ] ) );

                // 广播编码后的数据。服务器进行广播的消息会触发客户端的onmessage事件

                send_message ( $message );

                // 跳出foreach循环

                break 2;

            }

            // 删除已经关闭的Socket

            $buf = @socket_read ( $v, 1024, PHP_NORMAL_READ );

            if ($buf === false) {

                $key = array_search ( $v, $clients );

                socket_getpeername ( $v, $ip );

                unset ( $clients [$key] );

                $msg = mask ( json_encode ( [

                        'type' => 'system',

                        'content' => $ip . "已经下线。"

                ] ) );

                send_message ( $msg );

            }

        }

    }

}

// 发送消息的方法

function send_message($msg) {

    global $clients;

    foreach ( $clients as $changed_socket ) {

        @socket_write ( $changed_socket, $msg, strlen ( $msg ) );

    }

    return true;

}

// 以下3个函数，我们只需了解总体结构即可。在有需要时可以直接使用

// 解码数据。服务器解码客户端发送过来的数据

function unmask($text) {

    $length = ord ( $text [1] ) & 127;

    if ($length == 126) {

        $masks = substr ( $text, 4, 4 );

        $data = substr ( $text, 8 );

    } elseif ($length == 127) {

        $masks = substr ( $text, 10, 4 );

        $data = substr ( $text, 14 );

    } else {

        $masks = substr ( $text, 2, 4 );

        $data = substr ( $text, 6 );

    }

    $text = "";

    for($i = 0; $i < strlen ( $data ); ++ $i) {

        $text .= $data [$i] ^ $masks [$i % 4];

    }

    return $text;

}

// 编码数据。在服务器向客户端发送数据时需要将数据打包

function mask($text) {

    $b1 = 0x80 | (0x1 & 0x0f);

    $length = strlen ( $text );

    if ($length <= 125) {

        $header = pack ( 'CC', $b1, $length );

    } elseif ($length > 125 && $length < 65536) {

        $header = pack ( 'CCn', $b1, 126, $length );

    } elseif ($length >= 65536) {

        $header = pack ( 'CCNN', $b1, 127, $length );

    }

    return $header . $text;

}

// 握手的逻辑。客户端与服务端相互识别的过程

function perform_handshaking($receved_header, $client_conn, $host, $port) {

    $headers = array ();

    $lines = preg_split ( "/\r\n/", $receved_header );

    foreach ( $lines as $line ) {

        $line = chop ( $line );

        if (preg_match ( '/\A(\S+): (.*)\z/', $line, $matches )) {

            $headers [$matches [1]] = $matches [2];

        }

    }

    $secKey = $headers ['Sec-WebSocket-Key'];

    $secAccept = base64_encode ( pack ( 'H*', sha1 ( $secKey . '258EAFA5-E914-47DA-95CA-C5AB0DC85B11' ) ) );

    $upgrade = "HTTP/1.1 101 Web Socket Protocol Handshake\r\n" . "Upgrade: websocket\r\n" . "Connection: Upgrade\r\n" . "WebSocket-Origin: $host\r\n" . "Sec-WebSocket-Accept:$secAccept\r\n\r\n";

    socket_write ( $client_conn, $upgrade, strlen ( $upgrade ) );

}