Detailed explanation of TCP/IP data communication in Node.js

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1. Use the net module to implement TCP-based data communication

Provides a net module dedicated to realizing communication between the TCP server and the TCP client

1.1 Create a TCP server

Use the net module to create a TCP server in Node.js

var server = net.createServer([options],[connectionListener]) //options：false当TCP服务器接收到客户端发送的一个FIN包时将会回发一个FIN包 true当TCP服务器接收到客户端发送的一个FIN包时将不会回发FIN包，这使得TCP服务器可以继续向客户端发送数据，但不会继续接收客户端发送的数据。来发者必须调用end方法来关闭socket连接。默认为false connectionListener：指定当客户端与服务器端简历连接时所要调用的回调函数 function(socket){ //回调函数代码 }

The parameter value is the socket port object that the TCP server listens to. The createServer method returns the created TCP server

When the client establishes a connection with the server, the connection event is triggered. You can use the following method to execute the callback function

server.on('connection',function(socket){ //回调函数代码 })

After creating the TCP server, use the listen method to notify the server to start monitoring the client connection

server.listen(port,[host],[backlog],[callback]) //port指定需要监听的端口号， host：指定需要监听的IP地址或主机名，如果省略，服务器将监听来自于任何IPv4地址的客户端连接 backlog：指定位于等待队列中的客户端连接的最大数量 callback：无参回调函数 server.listen(path,[callback]) //server:代表一个使用unix端口的服务器 path：指定需要监听的路径，会触发listening事件，然后执行回调函数callback server.listenting（handle，[callback]） //server 代表一个TCP服务器 handle：指定需要监听的socket句柄（该句柄可以为一个TCP服务器对象，socket端口对象，文件描述符）

Here is an example to create a TCP server:

var net = require('net') var server = net.createServer(function(socket){ console.log('客户端与服务器连接已建立') }) server.listen(8431,'localhost',function(){ console.log('服务器端开始监听') })

After running, you can get the following results:

Use telnet to access the corresponding server:

telnet localhost 8431

The results that will appear are as follows:

socket port object example:

var net = require('net') var file = require('fs').createWriteStream('./message.txt'); var server = net.createServer(function(socket){ console.log('客户端与服务器连接已建立') server.getConnections(function(err,count){ console.log('当前存在%d个客户端连接。',count); server.maxConnections = 4; console.log('TCP服务器的最大连接数为%d',server.maxConnections); }) // server.close(function(){ // console.log('TCP服务器被关闭。'); // }) }) server.listen(8431,'localhost',function(){ console.log('服务器端开始监听') }) server.on('connection',function(socket){ address = socket.address(); console.log('被监视的地址信息为%j',address); socket.pipe(file); socket.setEncoding('utf8'); socket.on('data',function(data){ console.log(data.toString()); console.log('已接受到%d字节数据。',socket.bytesRead); }); socket.on('end',function(){ file.end('再见') console.log('客户端连接被关闭。') }) socket.pause(); setTimeout(function(){ console.log('*************') socket.resume(); socket.pipe(file,{end:false}); },30*1000); // socket.pipe(file,{end:false}); // setTimeout(function(){ // file.end('再见。'); // socket.unpipe(file); // },5000); socket.setTimeout(10*1000); socket.on('timeout',function(){ console.log('客户端连接超时'); socket.setTimeout(0); }) })

1.2 Create TCP client

Establish TCP client example:

var net = require("net"); var client = new net.Socket(); client.setEncoding('utf8'); client.connect(8431,'localhost',function(){ console.log('已连接到服务器'); client.write('你好'); console.log('当前已发送%d字节',client.bytesWritten); client.end('再见') console.log('当前已发送%d字节',client.bytesWritten); // setTimeout(function(){ // client.end('再见'); // },10*1000) }); client.on('data',function(data){ //console.log('已接收服务器端发送的数据： '+data); console.log('已接收服务器端发送的数据'); }) client.on('error',function(err){ console.log('与服务器连接或通信的过程中发生了一个错误，错误编码为%s',err.code); client.destroy(); })

At the same time, the corresponding server needs to be established:

var net = require('net'); var fs = require('fs'); var server = net.createServer(); server.on('connection',function(socket){ console.log('客户端与服务器端连接已建立'); socket.setEncoding('utf8'); var readStream = fs.createReadStream('./server.js'); readStream.on('data',function(data){ var flag = socket.write(data); console.log('write方法的返回值为：'+flag); console.log('缓存队列中当前缓存了%d字符。',socket.bufferSize); }) socket.on('data',function(data){ console.log('已连接客户端发送的数据:'+data); socket.write('确认数据：'+data); }) socket.on('error',function(err){ console.log('客户端通信的过程中发生了一个错误，错误编码为%s',err.code); socket.destroy(); }) socket.on('end',function(){ console.log('客户端连接被关闭。'); server.unref(); }) socket.on('close',function(had_error){ if(had_error){ console.log('由于一个错误导致socket端口被关闭。'); server.unref(); }else{ console.log('socket端口被正常关闭。'); } }) server.getConnections(function(err,count){ if(count==2) server.close(); }); }); server.listen(8431,'localhost'); server.on('close',function(){ console.log('TCP服务器被关闭。'); })

In Node.js, the following method can be used to continuously send detection packets to the client or server to determine the connection status;

socket.setKeepAlive([enable],[initialDelay]) //enable:true:启用Keep-alive机制，不断向对方发送一个探测包，如果没有回应表示连接关闭 initialDelay：间隔时间（毫秒）

Related recommendations:

Node.js creates Web and TCP servers

A brief analysis of the three-way handshake four of TCP transmission Wave strategy

What is the difference between TCP/IP and UDP

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