node.js 使用 net 模块模拟 websocket 握手进行数据传递操作示例

Request URL: ws://localhost:8888/
Request Method: GET
Connection: Upgrade
Upgrade: websocket
Sec-WebSocket-Version: 13
Sec-WebSocket-Key: uR5YP/BMO6M24tAFcmHeXw==
Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits

Status Code: 101 Switching Protocols
Connection: Upgrade
Sec-WebSocket-Accept: eS92kXpBNI6fWsCkj6WxH6QeoHs=
Upgrade: websocket

const crypto = require('crypto');
function getSecWebSocketAccept(key) {
  return crypto.createHash('sha1')
    .update(key + '258EAFA5-E914-47DA-95CA-C5AB0DC85B11')
    .digest('base64');
}
console.log(getSecWebSocketAccept('uR5YP/BMO6M24tAFcmHeXw=='));

0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-------+-+-------------+-------------------------------+
|F|R|R|R| opcode|M| Payload len |  Extended payload length  |
|I|S|S|S| (4) |A|   (7)   |       (16/64)      |
|N|V|V|V|    |S|       |  (if payload len==126/127)  |
| |1|2|3|    |K|       |                |
+-+-+-+-+-------+-+-------------+-------------------------------+
|   Extended payload length continued, if payload len == 127 |
+-------------------------------+-------------------------------+
|                |Masking-key, if MASK set to 1 |
+-------------------------------+-------------------------------+
| Masking-key (continued)    |     Payload Data     |
+-------------------------------+-------------------------------+
|           Payload Data continued ...        |
+---------------------------------------------------------------+
|           Payload Data continued ...        |
+---------------------------------------------------------------+

function unmask(buffer, mask) {
  const length = buffer.length;
  for (var i = 0; i < length; i++) {
    buffer[i] ^= mask[i & 3];
  }
}

const crypto = require('crypto');
const net = require('net');
//计算websocket校验
function getSecWebSocketAccept(key) {
  return crypto.createHash('sha1')
    .update(key + '258EAFA5-E914-47DA-95CA-C5AB0DC85B11')
    .digest('base64');
}
//掩码操作
function unmask(buffer, mask) {
  const length = buffer.length;
  for (var i = 0; i < length; i++) {
    buffer[i] ^= mask[i & 3];
  }
}
//创建一个tcp服务器
let server = net.createServer(function (socket) {
  socket.once('data', function (data) {
    data = data.toString();
    //查看请求头中是否有升级websocket协议的头信息
    if (data.match(/Upgrade: websocket/)) {
      let rows = data.split('\r\n');
      //去掉第一行的请求行
      //去掉请求头的尾部两个空行
      rows = rows.slice(1, -2);
      let headers = {};
      rows.forEach(function (value) {
        let [k, v] = value.split(': ');
        headers[k] = v;
      });
      //判断websocket的版本
      if (headers['Sec-WebSocket-Version'] == 13) {
        let secWebSocketKey = headers['Sec-WebSocket-Key'];
        //计算websocket校验
        let secWebSocketAccept = getSecWebSocketAccept(secWebSocketKey);
        //服务端响应的内容
        let res = [
          'HTTP/1.1 101 Switching Protocols',
          'Upgrade: websocket',
          `Sec-WebSocket-Accept: ${secWebSocketAccept}`,
          'Connection: Upgrade',
          '\r\n'
        ].join('\r\n');
        //给客户端发送响应内容
        socket.write(res);
        //注意这里不要断开连接，继续监听'data'事件
        socket.on('data', function (buffer) {
          //注意buffer的最小单位是一个字节
          //取第一个字节的第一位，判断是否是结束位
          let fin = (buffer[0] & 0b10000000) === 0b10000000;
          //取第一个字节的后四位，得到的一个是十进制数
          let opcode = buffer[0] & 0b00001111;
          //取第二个字节的第一位是否是1，判断是否掩码操作
          let mask = buffer[1] & 0b100000000 === 0b100000000;
          //载荷数据的长度
          let payloadLength = buffer[1] & 0b01111111;
          //掩码键，占4个字节
          let maskingKey = buffer.slice(2, 6);
          //载荷数据，就是客户端发送的实际数据
          let payloadData = buffer.slice(6);
          //对数据进行解码处理
          unmask(payloadData, maskingKey);
          //向客户端响应数据
          let send = Buffer.alloc(2 + payloadData.length);
          //0b10000000表示发送结束
          send[0] = opcode | 0b10000000;
          //载荷数据的长度
          send[1] = payloadData.length;
          payloadData.copy(send, 2);
          socket.write(send);
        });
      }
    }
  });
  socket.on('error', function (err) {
    console.log(err);
  });
  socket.on('end', function () {
    console.log('连接结束');
  });
  socket.on('close', function () {
    console.log('连接关闭');
  });
});
//监听8888端口
server.listen(8888);

<!doctype html>
<html lang="zh-CN">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
</head>
<body>
<script>
  var ws = new WebSocket('ws://localhost:8888');
  ws.onopen = function () {
    console.log('连接成功');
    ws.send('你好服务端');
  };
  ws.onmessage = function (ev) {
    console.log('接收数据', ev.data);
  };
  ws.onclose = function () {
    console.log('连接断开');
  };
</script>
</body>
</html>