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Node js http module

http module is used to transfer data over the Hyper Text Transfer Protocol (HTTP). For example it can create an http server to listen to a specific port and provide response to the client.

Example 1

Here is an example of http server that listens on port 8080 and displays a message on the webpage.
  • http.createServer method creates the server object.
  • req and res represent request and response.
  • res.writeHead can be used to provide the response status code,  status message or headers to the browser
  • res.write is used to write the part of the html page body.
  • res.end method signals the server that the response has been sent completely.
  • In the example below the server is listening to port 8080. So the local host url to access the server would be http://localhost:8080
serverDisplayText.js:
var http = require('http');

const server = http.createServer(function (req, res) {
  res.writeHead(200, { 'Content-Type': 'text/html' });
  res.write('Hello World!'); //write a response to the client
  res.end();
})

server.listen(8080);

console.log('server running on port 8080');
Running the code:
PS C:\Users\mail2\Downloads\httpServer> node serverDisplayText
server running on port 8080
http://localhost:8080
Hello World!

Example 2

Here is another http server example. The server displays different HTML files in the response based on the url user enters.
  • html pages home.html and about.html are stored under "pages" folder in the same directory as the JavaScript file serverDisplayHTML.js
  • url module is used to get the url path
  • fs module is used to get the content from the html files.
  • Server listens on port 8081
serverDisplayHTML.js:
const http = require('http');
const fs = require('fs');
const url = require('url');

const server = http.createServer((req, res) => {
    let pathname = url.parse(req.url).pathname;
    console.log(`Request for ${pathname} received`);
    if (pathname == '/') {
        pathname = '/home';
    }
    fs.readFile('pages/' + pathname.substr(1) + '.html', (err, data) => {
        if (err) {
            console.error(err);
            res.writeHead(404, { 'Content-Type': 'text/plain' });
            res.write('404 - file not found');
        } else {
            res.writeHead(200, { 'Content-Type': 'text/html' });
            res.write(data.toString());
        }
        res.end();
    });
});

server.listen(8081);
console.log('server running on port 8081');
home.html :
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Home page</title>
</head>
<body style="background-color: rgb(236, 230, 230)">

    <div style="background-color: rgb(255, 255, 255); border-radius: 10px; margin: auto; border: 2px solid gray; padding: 50px; margin: 50px;">
        This is home page.
    </div>
</body>
</html>
about.html :
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>About page</title>
</head>
<body style="background-color: rgb(236, 230, 230)">

    <div style="background-color: rgb(255, 255, 255); border-radius: 10px; margin: auto; border: 2px solid gray; padding: 50px; margin: 50px;">
        This is about page.
    </div>
</body>
</html>
Running the code :
PS C:\Users\mail2\Downloads\httpServer> node serverDisplayHTML
server running on port 8081

Example 3

Below code provides JSON in the response to the request.
  • url module is used to get the query parameters.
serverDisplayJson.js :
const http = require('http');
var url = require('url');

const server = http.createServer((req, res) => {

    var q = url.parse(req.url, true).query;

    if ((q.name != null) || (q.year != null)) {

        res.writeHead(200, { 'Content-Type': 'application/json' });
        res.write(JSON.stringify({ name: q.name,  year: q.year,}));
        res.end();

    } else {

        res.end('Invalid request');
    }
});

server.listen(8082);

console.log('server running on port 8082');
Running the code:
PS C:\Users\mail2\Downloads\httpServer> node serverDisplayJson
server running on port 8082
http://localhost:8082/?name=Adam&&year=2014 
{"name":"Adam","year":"2014"}




Source Code:
https://github.com/it-code-lab/nodejs-http-module


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