【NodeJs】使用TCP套接字收发数据的简单实例

因为TCP协议是流协议，在收发数据的时候会有粘包的问题。本例使用自定义的SPtcp封包协议对TCP数据再进行一次封装，解决了粘包问题。

注：其性能仍有待优化。优化方向：使用TCP自带的接收窗口缓存。

• sptcp.js

/**
 * script: sptcp.js
 * description: 简单封包协议SPtcp类
 * authors: alwu007@sina.cn
 * date: 2016-04-14
 */

var util = require('util');

function SPtcp(socket) {
    //解析所处的阶段
    var _sp_parse_step = SPtcp.SP_PARSE_STEP.HEADER;
    //接收缓存
    var _sp_rcv_buf = new Buffer(0);
    //包头
    var _sp_header = null;
    //包体
    var _sp_body = null;
    //套接字
    this.socket = socket;

    //解析整包方法
    function _spParseSPPacket(func){
        if (_sp_rcv_buf.length >= SPtcp.SP_HEADER_LENGTH) {
            //解析包头
            _sp_header = {bodyLength: _sp_rcv_buf.readUInt16LE(0, true)};
            //裁剪接收缓存
            _sp_rcv_buf = _sp_rcv_buf.slice(SPtcp.SP_HEADER_LENGTH);
            //解析包体
            _sp_parse_step = SPtcp.SP_PARSE_STEP.BODY;
            _spParseBody(func);
        }
    };

    //解析包体方法
    function _spParseBody(func){
        if (_sp_rcv_buf.length >= _sp_header.bodyLength) {
            var packet = _sp_rcv_buf.toString('utf8', 0, _sp_header.bodyLength);
            util.log('['+socket.remoteAddress+']->['+socket.localAddress+'] receive: '+packet);
            //裁剪接收缓存
            _sp_rcv_buf = _sp_rcv_buf.slice(_sp_header.bodyLength);
            //处理消息
            try {
                var msg = JSON.parse(packet);
                func(msg);
            } catch(e) {
                util.log(e);
            }
            //清空包头和包体
            _sp_header = null;
            _sp_body = null;
            //解析下一个包
            _sp_parse_step = SPtcp.SP_PARSE_STEP.HEADER;
            _spParseSPPacket(func);
        }
    };

    //接收数据
    this.spReceiveData = (data, func) => {
        if (!func) func = msg => undefined;
        //合并新旧数据
        _sp_rcv_buf = Buffer.concat([_sp_rcv_buf, data]);
        //解析处理数据
        if (_sp_parse_step == SPtcp.SP_PARSE_STEP.HEADER) {
            _spParseSPPacket(func);
        } else if (_sp_parse_step == SPtcp.SP_PARSE_STEP.BODY) {
            _spParseBody(func);
        }
    };

    //发送数据
    this.spSendData = msg => {
        var packet = JSON.stringify(msg);
        var body_buf = new Buffer(packet);
        var head_buf = new Buffer(SPtcp.SP_HEADER_LENGTH);
        head_buf.writeUInt16LE(body_buf.length);
        var snd_buf = Buffer.concat([head_buf, body_buf]);
        this.socket.write(snd_buf);
    };

    //销毁方法
    this.spDestroy = () => {
        delete this.socket;
    };
}

//包头长度，单位字节
SPtcp.SP_HEADER_LENGTH = 4;
//解析所处的阶段
SPtcp.SP_PARSE_STEP = {
    HEADER: 0,  //解析包头阶段
    BODY: 1,    //解析包体阶段
};

exports.SPtcp = SPtcp;

• spsvr.js

/**
 * script: spsvr.js
 * description: SPtcp服务器端
 * authors: alwu007@sina.cn
 * date: 2016-04-15
 */

var util = require('util');
var net = require('net');
var SPtcp = require('./sptcp').SPtcp;

var server = net.createServer(client => {
    util.log('client connected: ' + client.remoteAddress);
    //套接字继承SPtcp
    SPtcp.call(client, client);
    //监听data事件
    client.on('data', data => {
        client.spReceiveData(data, msg => {
            util.log('susl msg: ' + util.inspect(msg));
            client.spSendData(msg);
        });
    });
    //监听结束事件
    client.on('end', () => {
        util.log('disconnected from client: ' + client.remoteAddress);
        client.spDestroy();
    });
    //监听错误事件
    client.on('error', err => {
        util.log(err);
        client.end();
    });
});

var listen_options = {
    host: '172.16.200.26',
    port: 6200,
};
util.log('listen options: ' + util.inspect(listen_options));
server.listen(listen_options, () => {
    util.log('server bound');
});

• spcli.js

/**
 * script: spcli.js
 * description: SPtcp客户端
 * authors: alwu007@sina.cn
 * date: 2016-04-15
 */

var util = require('util');
var net = require('net');
var SPtcp = require('./sptcp').SPtcp;

var connect_options = {
    host: '172.16.200.26',
    port: 6200,
    localPort: 6201,
};
util.log('connect options: ' + util.inspect(connect_options));
var client = net.connect(connect_options, ()=>{
    //套接字继承SPtcp
    SPtcp.call(client, client);
    //监听data事件
    client.on('data', data => {
        client.spReceiveData(data, msg => {
            util.log('susl msg: ' + util.inspect(msg));
        });
    });
    //监听结束事件
    client.on('end', () => {
        util.log('disconnected from server: ' + client.remoteAddress);
        client.spDestroy();
    });
    //监听错误事件
    client.on('error', err => {
        util.log(err);
        client.end();
    });
    //发送消息
    for (var i=0; i<10; i++) {
        var msg = {op:'test', msg:'hello, 草谷子!', times:i};
        client.spSendData(msg);
    }
    //关闭连接
    client.end();
});

优化方案1：接收缓存_sp_rcv_buf改为Buffer数组，并记录数组元素的长度和_sp_rcv_length。这样做的好处有两点，一点是不用每次收到数据就执行一次concat方法分配一块新的内存；一点是在执行concat方法时直接传入长度参数，加快该方法的执行速度。——于2016-04-16

优化方案2：将类的方法定义在prototype原型对象上，这样该类的所有实例就共用同一个方法副本，节约资源。——于2016-04-19