Socket.IO communication is based on named events.

An event consists of an event name and optional data.

For example:

socket.emit('hello', 'John');

The client emits an event called hello with the value John.

The server receives it using:

socket.on('hello', (name) => {
  console.log(name);
});

The same concept works in the opposite direction. The server can emit events that the browser listens for.

Important methods:

Method	Purpose
socket.emit()	Sends an event
socket.on()	Registers an event listener
socket.once()	Registers a listener that runs once
socket.off()	Removes an event listener
io.emit()	Sends an event to all connected clients

Use meaningful event names such as chat:send, chat:message, and user:joined instead of generic names such as event1.