Here is the HTTP web server we used as the Node Hello World application:

const http = require('http')

const hostname = 'localhost'
const port = 3000

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

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

Let’s analyze it briefly. We include the http module.

We use the module to create an HTTP server.

The server is set to listen on the specified hostname, localhost, on port 3000. When the server is ready, the listen callback function is called.

The callback function we pass is the one that’s going to be executed upon every request that comes in. Whenever a new request is received, the request event is called, providing two objects: a request (an http.IncomingMessage object) and a response (an http.ServerResponse object).

request provides the request details. Through it, we access the request headers and request data.

response is used to populate the data we’re going to return to the client.

In this case with

res.statusCode = 200

we set the statusCode property to 200, to indicate a successful response.

We also set the Content-Type header:

res.setHeader('Content-Type', 'text/plain')

and we end close the response, adding the content as an argument to end():

res.end('Hello World\n')

Lessons in this unit:

0:	Introduction
1:	Installing Node.js on your computer
2:	How to write your first Node.js program
3:	Importing other files
4:	Using npm to install packages
5:	Using built-in modules
6:	How to use the Node.js REPL
7:	Reading files with Node
8:	Writing files with Node
9:	▶︎ Build an HTTP Server
10:	The Node Event emitter
11:	How to read environment variables from Node.js
12:	Node Buffers
13:	Node.js Streams
14:	How to use promises and await with Node.js callback-based functions
15:	Modern package managers (pnpm and Bun)