PHP实现WebSocket实例详解

WebSocket 是一种在单个TCP连接上进行全双工通信的协议。它是一个HTML5新技术，能够使Web应用程序实现实时通讯功能。在Web开发中，常常需要用到WebSocket实现实时消息推送等功能。

本篇文章将会详细讲解如何使用 PHP 实现 WebSocket。

实现步骤

1. 建立WebSocket连接

WebSocket 连接首先要发送一个 HTTP 请求，在请求头中包含升级为 WebSocket 的协议信息。在 PHP 中，可以通过手动构造响应头来完成 WebSocket 的升级。

代码示例1：建立WebSocket连接

<?php

$host = 'localhost';
$port = 8080;

$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
socket_bind($socket, $host, $port);
socket_listen($socket);

$client = socket_accept($socket);

$headers = '';
$buffer = '';
while (strpos($headers, "\r\n\r\n") === false) {
    $buffer = socket_read($client, 1024);
    $headers .= $buffer;
}

parse_str($buffer);
$key = base64_encode(sha1($sec_websocket_key . '258EAFA5-E914-47DA-95CA-C5AB0DC85B11', true));

$response = "HTTP/1.1 101 Switching Protocols\r\n";
$response .= "Upgrade: websocket\r\n";
$response .= "Connection: Upgrade\r\n";
$response .= "Sec-WebSocket-Accept: " . $key . "\r\n";

socket_write($client, $response);

// 此时 WebSocket 连接已成功建立

2. 与客户端通信

WebSocket 的通信需要使用特殊的数据帧格式，包括FIN、RSV1、RSV2、RSV3、opcode、Mask、Payload length、Masking key、Payload data 等字段。通过解析这些数据帧，我们就可以实现与客户端的通信。

代码示例2：与客户端通信

<?php

function decode($client, $data)
{
    $bytes = strlen($data);
    if ($bytes < 2) {
        return false;
    }

    $opcode = ord($data[0]) & 0xf;
    $fin = (ord($data[0]) >> 7) & 0x1;
    $has_mask = (ord($data[1]) >> 7) & 0x1;
    $payload_len = ord($data[1]) & 0x7f;
    $offset = 2;

    if ($payload_len == 126) {
        if ($bytes < 4) {
            return false;
        }
        $payload_len = ord($data[2]) * 256 + ord($data[3]);
        $offset += 2;
    } elseif ($payload_len == 127) {
        if ($bytes < 10) {
            return false;
        }
        $payload_len = ord($data[2]) * 65536 * 65536 * 256 + ord($data[3]) * 65536 * 65536 + ord($data[4]) * 65536 * 256 + ord($data[5]) * 65536 + ord($data[6]) * 256 + ord($data[7]);
        $offset += 8;
    }

    if ($has_mask) {
        if ($bytes < $offset + 4) {
            return false;
        }
        $mask_key = substr($data, $offset, 4);
        $offset += 4;
    }

    if ($bytes < $offset + $payload_len) {
        return false;
    }

    $payload_data = substr($data, $offset, $payload_len);
    if ($has_mask) {
        for ($i = 0; $i < $payload_len; $i++) {
            $payload_data[$i] = $payload_data[$i] ^ $mask_key[$i % 4];
        }
    }

    return array(
        'fin' => $fin,
        'opcode' => $opcode,
        'payload_data' => $payload_data,
    );
}

function encode($payload_data, $opcode = 1, $fin = true)
{
    $data = '';
    switch ($opcode) {
        case 1:
            $data .= $fin ? "\x81" : "\x01";
            break;
        case 2:
            $data .= $fin ? "\x82" : "\x02";
            break;
    }
    $length = strlen($payload_data);
    if ($length <= 125) {
        $data .= chr($length);
    } elseif ($length <= 65535) {
        $data .= chr(126) . pack('n', $length);
    } else {
        $data .= chr(127) . pack('N', 0) . pack('N', $length);
    }
    $data .= $payload_data;

    return $data;
}

$host = 'localhost';
$port = 8080;

$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
socket_bind($socket, $host, $port);
socket_listen($socket);

$client = socket_accept($socket);

$headers = '';
$buffer = '';
while (strpos($headers, "\r\n\r\n") === false) {
    $buffer = socket_read($client, 1024);
    $headers .= $buffer;
}

parse_str($buffer);
$key = base64_encode(sha1($sec_websocket_key . '258EAFA5-E914-47DA-95CA-C5AB0DC85B11', true));

$response = "HTTP/1.1 101 Switching Protocols\r\n";
$response .= "Upgrade: websocket\r\n";
$response .= "Connection: Upgrade\r\n";
$response .= "Sec-WebSocket-Accept: " . $key . "\r\n";

socket_write($client, $response);

while (true) {
    $data = socket_read($client, 1024);
    $message = decode($client, $data);
    if (!$message) {
        break;
    }
    $payload_data = strtoupper($message['payload_data']);
    $response = encode($payload_data, $message['opcode'], true);
    socket_write($client, $response);
}

// 与客户端通信结束

小结

WebSocket 协议支持实时通讯功能，是 Web 开发中非常重要的一项技术。本文介绍了如何使用 PHP 实现 WebSocket，让我们可以掌握该技术的实现方法，为后续的开发工作奠定基础。