How to Create HTTP Server in Node.js: Simple Guide

To create an HTTP server in Node.js, use the built-in http module and call http.createServer() with a request handler function. Then, call server.listen(port) to start the server listening on a specific port.

Syntax

The basic syntax to create an HTTP server in Node.js involves importing the http module, creating a server with a callback function to handle requests and responses, and then starting the server to listen on a port.

• http.createServer(requestListener): Creates the server where requestListener is a function with request and response parameters.
• server.listen(port, callback): Starts the server on the given port. The optional callback runs when the server is ready.

javascript

const http = require('http');

const server = http.createServer((req, res) => {
  // handle request and response here
});

server.listen(3000, () => {
  console.log('Server is running on port 3000');
});

Example

This example creates a simple HTTP server that responds with "Hello, world!" to every request. It listens on port 3000 and logs a message when ready.

javascript

const http = require('http');

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

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

Output

Server running at http://localhost:3000/

Common Pitfalls

Common mistakes when creating an HTTP server in Node.js include:

• Not calling res.end(), which leaves the response hanging and the client waiting forever.
• Forgetting to set the Content-Type header, which can cause browsers to misinterpret the response.
• Trying to listen on a port already in use, which causes an error.
• Not handling errors on the server, which can crash the app.

Always ensure you end the response and handle errors gracefully.

javascript

/* Wrong: Missing res.end() */
const http = require('http');
const server = http.createServer((req, res) => {
  res.statusCode = 200;
  res.setHeader('Content-Type', 'text/plain');
  res.write('Hello');
  // Missing res.end() here causes the client to wait forever
});

server.listen(3000);

/* Right: Always call res.end() */
const serverFixed = http.createServer((req, res) => {
  res.statusCode = 200;
  res.setHeader('Content-Type', 'text/plain');
  res.end('Hello');
});

serverFixed.listen(3001);

Quick Reference

Remember these key points when creating an HTTP server in Node.js:

• Use http.createServer() with a request handler.
• Always call res.end() to finish the response.
• Set appropriate headers like Content-Type.
• Listen on an available port with server.listen(port).
• Handle errors to keep the server stable.

Key Takeaways

Use the built-in http module and createServer() to make an HTTP server.

Always end the response with res.end() to avoid hanging requests.

Set the Content-Type header to tell the client what data is sent.

Listen on a free port and handle errors to keep your server running.

Test your server by visiting http://localhost:port in a browser.