Detaillierte Erläuterung des Websocket-Protokolls
Informationen darüber, wofür das Websocket-Protokoll verwendet wird, finden Sie in anderen Artikeln.
WebSocket-Schlüsselwörter
HTML5-Protokoll, Echtzeit, Vollduplex-Kommunikation, lange Verbindung
Vorteile von WebSocket gegenüber herkömmlichem HTTP
1 Der Server stellt nur eine TCP-Verbindung her und kann weniger Verbindungen verwenden
2. Der WebSocket-Server kann Daten an den Client übertragen, z. B. Wertpapierinformationen in Echtzeit an den Client zurückmelden (dies ist sehr kritisch), real -Zeitliche Wetterdaten, flexibler als der HTTP-Request-Response-Modus
3. Leichterer Protokollheader, reduziert die Menge der Datenübertragung
Datenrahmenformat
Das Bild Unten wird das handgefertigte Datenrahmenformat
/** * fin |masked | | * srv1 | length | | * srv2 | (7bit |mask数据 |payload * srv3 | 7+2字节 | 4字节 |真实数据 opcode | 7+64字节 | | *（4bit） */
wie folgt erklärt:
1. Die ersten 8 Bits (ein Byte)
– fin: Ob die Datenübertragung erfolgt abgeschlossen ist, wird es als 1 gesendet. Abgeschlossen ist 0 und der Versand ist nicht abgeschlossen.
– srv1, srv2, srv3: für spätere Verwendung reserviert
– Opcode: Datentyp-Opcode, 4-Bit-Darstellung, wobei
TEXT: 1, Texttyp-String
BINÄR:
2. Binärdaten, die normalerweise zum Speichern von Bildern verwendet werden
SCHLIESSEN: 8. Schließen Sie den verbundenen Datenrahmen.
PING: 9, Herzschlagerkennung. ping
PONG:
10. Herzschlagerkennung. pong
var events = require('events');
var http = require('http');
var crypto = require('crypto');
var util = require('util');
/**
* 数据类型操作码 TEXT 字符串
* BINARY 二进制数据 常用来保存照片
* PING,PONG 用作心跳检测
* CLOSE 关闭连接的数据帧 (有很多关闭连接的代码 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']);
/**
* 写头
*/ 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');
/**
* 接收数据
*/
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连接继承事件
util.inherits(WebSocketConnection, events.EventEmitter);
/*
发送数据函数
* */
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;
//创造一个utf8的编码 可以被编码为字符串
payload = new Buffer(obj, 'utf8');
} else {
throw new Error('cannot send object.Must be string of Buffer');
}
this._doSend(opcode, payload); };
/* 关闭连接函数 * */
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);
//读取数据帧的前8bit
var fin = b1 & 0x80;
//如果为0x80，则标志传输结束
var opcode = b1 & 0x0f;//截取第一个字节的后四位
var b2 = buf.readUInt8(1);//读取数据帧第二个字节
var mask = b2 & 0x80;//判断是否有掩码，客户端必须要有
var length = b2 | 0x7f;//获取length属性 也是小于126数据长度的数据真实值
if (length > 125) {
if (buf.length < 8) {
return;//如果大于125，而字节数小于8，则显然不合规范要求
}
}
if (length === 126) {//获取的值为126 ，表示后两个字节用于表示数据长度
length = buf.readUInt16BE(2);//读取16bit的值
idx += 2;//+2
} else if (length === 127) {//获取的值为126 ，表示后8个字节用于表示数据长度
var highBits = buf.readUInt32BE(2);//(1/0)1111111
if (highBits != 0) {
this.close(1009, "");//1009关闭代码，说明数据太大
}
length = buf.readUInt32BE(6);//从第六到第十个字节为真实存放的数据长度
idx += 8;
}
if (buf.length < idx + 4 + length) {//不够长 4为掩码字节数
return;
}
var maskBytes = buf.slice(idx, idx + 4);//获取掩码数据
idx += 4;//指针前移到真实数据段
var payload = buf.slice(idx, idx + length);
payload = unmask(maskBytes, payload);//解码真实数据
this._handleFrame(opcode, payload);//处理操作码
this.buffer = buf.slice(idx + length);//缓存buffer
return true; };
/**
* 针对不同操作码进行不同处理
* @param 操作码
* @param 数据
*/
WebSocketConnection.prototype._handleFrame = function (opcode, buffer) {
"use strict";
var payload;
switch (opcode) {
case opcodes.TEXT:
payload = buffer.toString('utf8');//如果是文本需要转化为utf8的编码
this.emit('data', opcode, payload);//Buffer.toString()默认utf8 这里是故意指示的
break;
case opcodes.BINARY: //二进制文件直接交付
payload = buffer;
this.emit('data', opcode, payload);
break;
case opcodes.PING://发送ping做响应
this._doSend(opcodes.PING, buffer);
break;
case opcodes.PONG: //不做处理
break;
case opcodes.CLOSE://close有很多关闭码
let code, reason;//用于获取关闭码和关闭原因
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');
}
};
/**
* 实际发送数据的函数
* @param opcode 操作码
* @param payload 数据
* @private
*/
WebSocketConnection.prototype._doSend = function (opcode, payload) {
"use strict";
this.socket.write(encodeMessage(opcode, payload));//编码后直接通过socket发送 };
/**
* 编码数据
* @param opcode 操作码
* @param payload 数据
* @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);//读前8bit
buf.writeUInt8(b2, 1);//读8―15bit
//Buffer.prototype.copy = function(targetBuffer, targetStart, sourceStart, sourceEnd) {
payload.copy(buf, 2)//复制数据,从2(第三)字节开始
} 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;
};
/**
* 解掩码
* @param maskBytes 掩码数据
* @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);
};
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