/** * fin  |masked    |      | * srv1 |  length   |      | * srv2 |  (7bit   |mask數據   |payload * srv3 |   7+2字節  | 4字節    |真實數據 opcode |   7+64字節 |      | *（4bit） */

var events = require('events');var http = require('http');var crypto = require('crypto');var util = require('util');/** * 數據類型操作碼 TEXT 字符串 * BINARY 二進制數據 常用來保存照片 * PING,PONG 用作心跳檢測 * CLOSE 關閉連接的數據幀 (有很多關閉連接的代碼 1001，1009,1007,1002) */var opcodes = {  TEXT: 1,  BINARY: 2,  CLOSE: 8,  PING: 9,  PONG: 10};var WebSocketConnection = function (req, socket, upgradeHead) {  "use strict";  var self = this;  var key = hashWebSocketKey(req.headers['sec-websocket-key']);  /**   * 寫頭   */  socket.write('HTTP/1.1 101 Web Socket Protocol Handshake /r/n' +    "Upgrade:WebSocket/r/n" +    "Connection : Upgrade/r/n" +    "sec-websocket-accept: " + key + '/r/n/r/n');  /**   * 接收數據   */  socket.on('data', function (buf) {    self.buffer = Buffer.concat([self.buffer, buf]);    while (self._processBuffer()) {    }  });  socket.on('close', function (had_error) {    if (!self.closed) {      self.emit("close", 1006);      self.closed = true;    }  });  this.socket = socket;  this.buffer = new Buffer(0);  this.closed = false;};//websocket連接繼承事件util.inherits(WebSocketConnection, events.EventEmitter);/* 發送數據函數 * */WebSocketConnection.prototype.send = function (obj) {  "use strict";  var opcode;  var payload;  if (Buffer.isBuffer(obj)) {    opcode = opcodes.BINARY;    payload = obj;  } else if (typeof obj) {    opcode = opcodes.TEXT;    //創造一個utf8的編碼 可以被編碼為字符串    payload = new Buffer(obj, 'utf8');  } else {    throw new Error('cannot send object.Must be string of Buffer');  }  this._doSend(opcode, payload);};/* 關閉連接函數 * */WebSocketConnection.prototype.close = function (code, reason) {  "use strict";  var opcode = opcodes.CLOSE;  var buffer;  if (code) {    buffer = new Buffer(Buffer.byteLength(reason) + 2);    buffer.writeUInt16BE(code, 0);    buffer.write(reason, 2);  } else {    buffer = new Buffer(0);  }  this._doSend(opcode, buffer);  this.closed = true;};WebSocketConnection.prototype._processBuffer = function () {  "use strict";  var buf = this.buffer;  if (buf.length < 2) {    return;  }  var idx = 2;  var b1 = buf.readUInt8(0);  //讀取數據幀的前8bit  var fin = b1 & 0x80; //如果為0x80，則標志傳輸結束  var opcode = b1 & 0x0f;//截取第一個字節的后四位  var b2 = buf.readUInt8(1);//讀取數據幀第二個字節  var mask = b2 & 0x80;//判斷是否有掩碼，客戶端必須要有  var length = b2 | 0x7f;//獲取length屬性 也是小于126數據長度的數據真實值  if (length > 125) {    if (buf.length < 8) {      return;//如果大于125，而字節數小于8，則顯然不合規范要求    }  }  if (length === 126) {//獲取的值為126 ，表示后兩個字節用于表示數據長度    length = buf.readUInt16BE(2);//讀取16bit的值    idx += 2;//+2  } else if (length === 127) {//獲取的值為126 ，表示后8個字節用于表示數據長度    var highBits = buf.readUInt32BE(2);//(1/0)1111111    if (highBits != 0) {      this.close(1009, "");//1009關閉代碼，說明數據太大    }    length = buf.readUInt32BE(6);//從第六到第十個字節為真實存放的數據長度    idx += 8;  }  if (buf.length < idx + 4 + length) {//不夠長 4為掩碼字節數    return;  }  var maskBytes = buf.slice(idx, idx + 4);//獲取掩碼數據  idx += 4;//指針前移到真實數據段  var payload = buf.slice(idx, idx + length);  payload = unmask(maskBytes, payload);//解碼真實數據  this._handleFrame(opcode, payload);//處理操作碼  this.buffer = buf.slice(idx + length);//緩存buffer  return true;};/** * 針對不同操作碼進行不同處理 * @param 操作碼 * @param 數據 */WebSocketConnection.prototype._handleFrame = function (opcode, buffer) {  "use strict";  var payload;  switch (opcode) {    case opcodes.TEXT:      payload = buffer.toString('utf8');//如果是文本需要轉化為utf8的編碼      this.emit('data', opcode, payload);//Buffer.toString()默認utf8 這里是故意指示的      break;    case opcodes.BINARY: //二進制文件直接交付      payload = buffer;      this.emit('data', opcode, payload);      break;    case opcodes.PING://發送ping做響應      this._doSend(opcodes.PING, buffer);      break;    case opcodes.PONG: //不做處理      break;    case opcodes.CLOSE://close有很多關閉碼      let code, reason;//用于獲取關閉碼和關閉原因      if (buffer.length >= 2) {        code = buffer.readUInt16BE(0);        reason = buffer.toString('utf8', 2);      }      this.close(code, reason);      this.emit('close', code, reason);      break;    default:      this.close(1002, 'unknown opcode');  }};/** * 實際發送數據的函數 * @param opcode 操作碼 * @param payload 數據 * @private */WebSocketConnection.prototype._doSend = function (opcode, payload) {  "use strict";  this.socket.write(encodeMessage(opcode, payload));//編碼后直接通過socket發送};/** * 編碼數據 * @param opcode 操作碼 * @param payload  數據 * @returns {*} */var encodeMessage = function (opcode, payload) {  "use strict";  var buf;  var b1 = 0x80 | opcode;  var b2;  var length = payload.length;  if (length < 126) {    buf = new Buffer(payload.length + 2 + 0);    b2 |= length;    //buffer ,offset    buf.writeUInt8(b1, 0);//讀前8bit    buf.writeUInt8(b2, 1);//讀8―15bit    //Buffer.prototype.copy = function(targetBuffer, targetStart, sourceStart, sourceEnd) {    payload.copy(buf, 2)//復制數據,從2(第三)字節開始  } else if (length < (1 << 16)) {    buf = new Buffer(payload.length + 2 + 2);    b2 |= 126;    buf.writeUInt8(b1, 0);    buf.writeUInt8(b2, 1);    buf.writeUInt16BE(length, 2)    payload.copy(buf, 4);  } else {    buf = new Buffer(payload.length + 2 + 8);    b2 |= 127;    buf.writeUInt8(b1, 0);    buf.writeUInt8(b2, 1);    buf.writeUInt32BE(0, 2)    buf.writeUInt32BE(length, 6)    payload.copy(buf, 10);  }  return buf;};/** * 解掩碼 * @param maskBytes 掩碼數據 * @param data payload * @returns {Buffer} */var unmask = function (maskBytes, data) {  var payload = new Buffer(data.length);  for (var i = 0; i < data.length; i++) {    payload[i] = maskBytes[i % 4] ^ data[i];  }  return payload;};var KEY_SUFFIX = '258EAFA5-E914-47DA-95CA-C5ABoDC85B11';/*equals to crypto.createHash('sha1').update(key+'KEY_SUFFIX').digest('base64') * */var hashWebSocketKey = function (key) {  "use strict";  var sha1 = crypto.createHash('sha1');  sha1.update(key + KEY_SUFFIX, 'ascii');  return sha1.digest('base64');};exports.listen = function (port, host, connectionHandler) {  "use strict";  var srv = http.createServer(function (req, res) {  });  srv.on('upgrade', function (req, socket, upgradeHead) {    "use strict";    var ws = new WebSocketConnection(req, socket, upgradeHead);    connectionHandler(ws);  });  srv.listen(port, host);};