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Version: 4.x

Project initialization

The first goal is to set up a simple HTML webpage that serves out a form and a list of messages. We’re going to use the Node.JS web framework express to this end. Make sure Node.JS is installed.

First let’s create a package.json manifest file that describes our project. I recommend you place it in a dedicated empty directory (I’ll call mine socket-chat-example).

{
  "name": "socket-chat-example",
  "version": "0.0.1",
  "description": "my first socket.io app",
  "type": "commonjs",
  "dependencies": {}
}
caution

The "name" property must be unique, you cannot use a value like "socket.io" or "express", because npm will complain when installing the dependency.

Now, in order to easily populate the dependencies property with the things we need, we’ll use npm install:

npm install express@4

Once it's installed we can create an index.js file that will set up our application.

const express = require('express');
const { createServer } = require('node:http');

const app = express();
const server = createServer(app);

app.get('/', (req, res) => {
  res.send('<h1>Hello world</h1>');
});

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

This means that:

  • Express initializes app to be a function handler that you can supply to an HTTP server (as seen in line 5).
  • We define a route handler / that gets called when we hit our website home.
  • We make the http server listen on port 3000.

If you run node index.js you should see the following:

A console saying that the server has started listening on port 3000

And if you point your browser to http://localhost:3000:

A browser displaying a big 'Hello World'

So far, so good!

info

You can run this example directly in your browser on: