Building a Simple Web Server

Serve real pages over HTTP with Node's built-in http module

Big Idea: A web server is a program that waits for requests and sends back responses. With Node.js you can build one in just a few lines — no extra software to install, because the http module already comes with Node.

By the end you will be able to:

create a server with http.createServer and make it listen on a port,
read the incoming request (req.url, req.method),
send back plain text or HTML with the right Content-Type,
always finish a response with res.end().

1. What is a web server? (an analogy)

Think of a restaurant. You (the client, usually a web browser) walk in and ask for something: "I'd like the home page, please." A waiter (the server) takes your order, goes to the kitchen, and brings back a plate. Your order is the request; the plate is the response.

A web server does exactly this, over and over, very fast. It listens for requests coming in on a port (like a numbered door — we will use door number 3000), and for each request it sends back a response: some text, an HTML page, an image, and so on.

Node.js is great for this because it can handle many requests without getting stuck waiting, and the tools to build a server are already built in.

2. The request-response cycle

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Every time you open a web page, this two-step dance happens:

The browser sends a request (for example: GET the page at /).
The server reads the request and sends back a response (for example: 200 OK, here is some HTML).

Building a Simple Web Server