How to Use HTTP Module in Node.js: Simple Guide

In Node.js, you use the http module to create a web server that listens for requests and sends responses. You start by importing http, then use http.createServer() to define how to handle requests, and finally call server.listen() to start the server.

Syntax

The http module provides the createServer() method to create a server. This method takes a callback function with request and response objects. You use response.write() to send data and response.end() to finish the response. Finally, server.listen(port) starts the server on a specified port.

javascript

const http = require('http');

const server = http.createServer((request, response) => {
  // Handle incoming requests
  response.write('Hello World');
  response.end();
});

server.listen(3000);

Example

This example creates a simple server that responds with 'Hello World' to every request. It listens on port 3000. When you visit http://localhost:3000 in your browser, you will see the message.

javascript

const http = require('http');

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

server.listen(3000, () => {
  console.log('Server running at http://localhost:3000/');
});

Output

Server running at http://localhost:3000/

Common Pitfalls

• Forgetting to call response.end() causes the client to wait forever.
• Not setting the Content-Type header can make browsers misinterpret the response.
• Using require('http') is necessary; forgetting it causes errors.
• Trying to listen on a port already in use will throw an error.

javascript

/* Wrong: Missing response.end() */
const http = require('http');
const server = http.createServer((req, res) => {
  res.write('Hello');
  // res.end() missing here
});
server.listen(3000);

/* Right: Include response.end() */
const server2 = http.createServer((req, res) => {
  res.write('Hello');
  res.end();
});
server2.listen(3001);

Quick Reference

Remember these key methods and properties when using the http module:

Method/Property	Description
http.createServer(callback)	Creates a new HTTP server with a request handler
server.listen(port)	Starts the server listening on the given port
response.write(data)	Sends data to the client
response.end()	Ends the response, signaling completion
response.setHeader(name, value)	Sets HTTP headers for the response
request.url	The URL path requested by the client
request.method	The HTTP method used (GET, POST, etc.)

Key Takeaways

Use http.createServer() with a callback to handle requests and responses.

Always call response.end() to complete the response and avoid hanging connections.

Set appropriate headers like Content-Type to inform the client about the response data.

Start the server with server.listen(port) to listen for incoming requests.

Check for port conflicts and handle errors when starting the server.