Creating a backend for a chat app using Socket.IO

We can now start implementing a chat app using Socket.IO. We will be developing the following functionality for our chat app:

• Emitting events to send chat messages from the client to the server
• Broadcasting chat messages from the server to all clients
• Joining rooms to send messages in
• Using acknowledgments to get information about a user

Let’s get started!

Emitting events to send chat messages from the client to the server

We’ll start by emitting a chat.message event from the client to the server. For now, we are going to emit this event right after connecting. Later, we are going to integrate this into a frontend. Follow these steps to send chat messages from the client and receive them on the server:

1. Edit backend/src/app.js and cut/remove the following code:

   io.on('connection', (socket) => {
     console.log('user connected:', socket.id)
     ...