nodejs startup setting port number

Node.js is a popular backend JavaScript runtime environment that allows developers to write server-side applications in JavaScript. If you are writing an actual production application using Node.js, you will need to set up a listening port number so that network clients can access your application.

By default, the Node.js program will listen to port number 3000, which is a commonly used port number. However, in actual development, we may need to specify a different port number to avoid conflicts with other running applications.

Setting the port number in Node.js is very simple. You only need to create an Express application instance in the program and set the port number to let the application listen to the specified port.

The following is a code example for setting the port number:

const express = require('express')
const app = express()

const port = 8000 // 设置端口号为 8000

app.get('/', (req, res) => {
  res.send('Hello, World!')
})

// 监听指定端口号，开始接受网络请求
app.listen(port, () => {
  console.log(`Server is running on port ${port}`)
})

In the above code, we specified the port number as 8000 through const port = 8000. Then in the app.listen function, specify the port number to listen through the parameter port. When we run this program, the Node.js server will start listening on the specified port number, waiting for a request from the client.

It should be noted that the port number must be an integer and must be a number in the range of 0 ~ 65535. If the port number you choose is already taken by another application, your Node.js application will not start. In this case, you need to specify another available port number and update the port number in the program.

In a real production environment, you should consider saving the port number in the configuration file rather than hardcoding it into the code. This way, you can easily change the port number without having to modify the application's code and avoid unnecessary errors caused by misoperation.

Node.js has excellent scalability and flexibility. Applications created with it can reuse any NPM package and Node.js module and can be easily integrated into any platform or environment. Although Node.js is a relatively young technology, it has become one of the go-to platforms for creating high-performance server-side applications.

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