How to detect whether a port is occupied in Node.js

This article mainly introduces you to the relevant information about using Node.js to detect whether the port is occupied. The article introduces it in detail through the example code. It has certain reference learning value for everyone's study or work. Friends who need it Let’s learn together with the editor below.

Preface

When I was learning tcp/ip, I often encountered some things related to ports. When I was writing about some things on the network Things, sometimes some ports in use are prompted: The port is occupied, ah ah, it is quite depressing, and then I want to figure it out. I won’t say much below, let’s take a look at the detailed introduction.

Nodejs detects whether the port is occupied

When opening a local service, there is a situation: the current port is already used by another project , causing the service to fail to start.

Then next, we use a simple ten lines of code to detect whether the port is already occupied.

Thinking

If we want to know whether the port is occupied, we can open a new service and listen to the port. If it is opened successfully, it will be The port is not occupied, otherwise the port is already in use by another program.

Now that we have the basic idea, let’s start writing code.

Basic code

portIsOccupied.js

var net = require('net')

// 检测端口是否被占用
function portIsOccupied (port) {
 // 创建服务并监听该端口
 var server = net.createServer().listen(port)

 server.on('listening', function () { // 执行这块代码说明端口未被占用
 server.close() // 关闭服务
 console.log('The port【' + port + '】 is available.') // 控制台输出信息
 })

 server.on('error', function (err) {
 if (err.code === 'EADDRINUSE') { // 端口已经被使用
  console.log('The port【' + port + '】 is occupied, please change other port.')
 }
 })
}

// 执行
portIsOccupied(1987)

Test

Execute node portIsOccupied.js, under normal circumstances it will output The port【1987】 is available.

Use ssr to set the current directory as a static server, about the use of ssr You can find https://github.com/jaywcjlove/ssr here.
ssr will open port 1987 by default.

At this time, execute node portIsOccupied.js again and output The port【1987】 is occupied, please change other port.

Let the program More perfect

So far, we have been able to detect whether the port is occupied.

However, if I want to detect another port, I have to change the port number of the file every time, which is quite troublesome.

So is there a more perfect implementation method? Of course!

In Nodejs, there is such a fun thing, process.argv, which is an array. The first two values ​​are the location of the node program and the location of the currently running file.

The magic is that when we run the program, the parameters passed can be obtained through process.argv.

For example, node portIsOccupied.js -p 1987, then -p and 1987 will be added to the end of the process.argv array.

Now that we know the principle, let’s write a more perfect program.

The console passes parameters to the program

Modify portIsOccupied(1987) to:

var port = 80 // 默认检测80端口
if (process.argv[2] === '-p') {
 port = parseInt(process.argv[3])
}
portIsOccupied(port)

Execution

Where [port] is the port you want to detect.

node portIsOccupied.js -p [port]

The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.

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