TCP, HTTP, and Node.js

TCP

TCP is used for communication between the computer, through the preparation of client and server chat code, for the server and client work steps have a deep understanding. To implement TCP in Node, a NET module is provided. The NET module gives you an asynchronous network encapsulation that includes the ability to create servers and clients (called streams).

Example Creating a TCP server

net.createServer(options,connectionListener);

Create a TCP service with a callback listener that will execute when the connection arrives.

The parameter socket passed in is a socket, which helps us to realize the session. The socket corresponding to each client is different. Is a Duplex duplex flow that supports both read and write operations.

server.listen()

You can set the port for the service to listen to, the host name, and the backlog server to handle the maximum number of requests. The default is 511. There are also callback functions that are called when the service is successfully started

let net = require('net');
let server = net.createServer(function(socket){
    ...
})
server.listen(8080,'localhost'.function(){
    console.log(`server start 8080`)
});Copy the code

You can then configure the server

Set the maximum number of links on a server

server.maxConnections = 6;Copy the code

Firing method when a connection is obtained

You want each request to come in with a hint of the maximum number of connections and the total number of connections

server.getConnections(function(err,count){socket.write(' The current maximum capacity${server.maxConnections}Now,${count}`)});Copy the code

Accept client data

Read client input

socket.on('data'.function(data){
    console.log(data); 
});Copy the code

Stop reading

socket.pause();Copy the code

Restore read

socket.resume();Copy the code

pipe&unpipe

When listening for input from the client, write the input from the client to the file content.

If there are two clients, there are two sockets, one of which is closed, and the other cannot be written in

let net = require('net');
let path = require('path');
let ws = require('fs').createWriteStream(path.join(__dirname,'./1.txt'));
let server = net.createServer(function(socket){
    socket.pipe(ws,{end:false}); // So you can set this writable stream not to closesetTimeout(function(){
        ws.end(); // 关闭可写流
        socket.unpipe(ws); // 取消管道，就不能传输了
    },5000)
});
server.listen(8080);Copy the code

Closing the Client

socket.end(); In addition to closing it manually, we can also call this method to close it.

Closing the Server

server.close();

The close event indicates that the server is no longer receiving new requests and the current one can continue to be used. The close event is executed when the client is completely shut down.

// The close event will only trigger server.on('close'.function(){
    console.log('Server down');
})Copy the code

server.unref();

Unref () does not trigger the close event, the server is closed only when all clients are closed, and can still be closed if someone comes in (with a new request).

Example Creating a TCP client

Net.createconnection is used to create connections on the server side

let net = require('net');

let socket = net.createConnection({port:8080},function(){
    socket.write('hello');
    socket.on('data'.function(data){
        console.log(data);
    });
});Copy the code

HTTP

Node also provides a module to implement HTTP, called HTTP module, which encapsulates the efficient HTTP server and HTTP client, similar to the USE of NET module.

Creating an HTTP Server

request

This event is emitted when a client request arrives.

The most commonly used event is the Request event, and HTTP provides a shortcut to this event: http.createserver ([requestListener]).

Parameters of the res the req

The parameter req passed in is the request, which is a readable stream, and res is the response, which is a writable stream. The request and response are parsed through the socket.

There are two ways to create an HTTP server

The first kind of

let http = require('http'); 
let server = http.createServer();
server.on('request'.function(req,res){
    req.on('end'.function(){
        res.write('hello');
        res.end('world');
    });
});
server.listen(8080);Copy the code

You could write it this way

let http = require('http');
let server = http.createServer(function(req,res){
  res.end('ok');
});
server.listen(8080);Copy the code

Shutting down the HTTP Server

let http = require('http');
let server = http.createServer(function(req,res){
});
server.on('close'.function(){
    console.log('Server down');
});
server.listen(8080,'127.0.0.1'.function(){
    console.log('Server listening! ') server.close(); / / close});Copy the code

Create an HTTP client

The HTTP module provides two functions, http.request and http.get, to make requests to the HTTP server as a client.

Http. request(options, callback) Initiates an HTTP request. It takes two arguments, option, which is an associative array-like object representing the request’s parameters, and callback, which is the request’s callback function.

let http = require('http');
let options = {
    hostname:'localhost',
    port:4000,
    path: '/',
    method:'get'// Tell the server what type of data I want to send you.'Content-Type':'application/x-www-form-urlencoded'.'Content-Length': 17}}letreq = http.request(options); // When the client receives a response from the server, req.on('response'.function(res){
    res.on('data'.function(chunk){
        console.log(chunk);
    });
});
req.end('name=renee&&age=18');Copy the code

Get (options, callback) The HTTP module also provides a simpler method for handling GET requests: http.get. It is a simplified version of HTTP.request, the only difference being that http.get automatically sets the request method to get and does not require a manual call to req.end().

var http = require('http');

http.createServer(function(req,res){}).listen(3000);

http.get('http://www.baidu.com/index.html'.function(res){
    console.log('get response Code :' + res.statusCode);
}).on('error'.function(e){
    console.log("Got error: " + e.message);
})Copy the code

TCP