Nodejs build http server

Node.js is a JavaScript runtime environment built on the Chrome V8 engine and is widely used in web application development. In Node.js, we can easily build an HTTP server and access the web pages on the server through the browser. This article will introduce how to use Node.js to build an HTTP server.

1. Install Node.js

First, we need to install the Node.js environment locally. You can go to the Node.js official website https://nodejs.org/ to download the latest version and install it. After the installation is complete, you can enter the following command on the command line to check whether the installation is successful:

node -v

If the version number of Node.js is displayed correctly, the installation is successful.

2. Create HTTP Server

Creating an HTTP server using Node.js is very simple. You only need to introduce the built-in "http" module of Node.js in a JavaScript file, create a server and listen to the specified port. The following is a simple example:

const http = require('http');

const hostname = '127.0.0.1';
const port = 3000;

const server = http.createServer((req, res) => {
    res.statusCode = 200;
    res.setHeader('Content-Type', 'text/plain');
    res.end('Hello World!
');
});

server.listen(port, hostname, () => {
    console.log(`Server running at http://${hostname}:${port}/`);
});

The above code creates an HTTP server and listens to port 3000. When a client accesses the server, it returns the "Hello World!" string.

3. Access HTTP Server

After starting the HTTP server, we can use the browser to access the server. Enter "http://localhost:3000" in the browser's address bar (if the server is not running locally, replace "localhost" with the server IP address) and you will see the browser display the "Hello World!" characters string.

4. Processing HTTP requests

The above example is just the simplest example. In fact, when processing HTTP requests, we need to process HTTP requests based on the content of the request header and request body. to generate the appropriate response. The http module of Node.js provides us with an API specifically for handling requests. For example, we can obtain the requested URL address through req.url and obtain the requested method through req.method. The following is an example of returning different messages according to different URL addresses:

const http = require('http');

const hostname = '127.0.0.1';
const port = 3000;

const server = http.createServer((req, res) => {
    res.statusCode = 200;
    res.setHeader('Content-Type', 'text/plain');
    if (req.url === '/about') {
        res.end('This is about page');
    } else if (req.url === '/contact') {
        res.end('This is contact page');
    } else {
        res.end('Hello World!
');
    }
});

server.listen(port, hostname, () => {
    console.log(`Server running at http://${hostname}:${port}/`);
});

Access "http://localhost:3000/about" in the browser, you will see the browser displaying the "This is about page" characters string; visit "http://localhost:3000/contact", you will see the browser display "This is contact page" string; visit "http://localhost:3000", you will see the browser display " Hello World!" string.

5. Processing POST requests

In addition to processing GET requests, we can also process POST requests and store the data passed by the client to the server. The http module of Node.js also provides us with an API for processing POST requests. The following is a simple POST request processing example:

const http = require('http');

const hostname = '127.0.0.1';
const port = 3000;

const server = http.createServer((req, res) => {
    if (req.method === 'POST') {
        let body = '';
        req.on('data', chunk => {
            body += chunk.toString();
        });
        req.on('end', () => {
            console.log(`Received data: ${body}`);
            res.end('Data received');
        });
    } else {
        res.statusCode = 200;
        res.setHeader('Content-Type', 'text/plain');
        res.end('Hello World!
');
    }
});

server.listen(port, hostname, () => {
    console.log(`Server running at http://${hostname}:${port}/`);
});

When processing the HTTP request, the above code first determines whether the request method is POST. If it is POST, it monitors the data transfer event and stores the transferred data in the body. variable and print it out after the data transmission is completed. In the client HTML file, you can use the

<!DOCTYPE html>
<html>
<head>
    <title>POST Request Example</title>
</head>
<body>
    <form action="http://localhost:3000" method="post">
        <label for="name">Name:</label>
        <input type="text" id="name" name="name"><br><br>
        <label for="email">Email:</label>
        <input type="email" id="email" name="email"><br><br>
        <input type="submit" value="Submit">
    </form>
</body>
</html>