Before using Socket.IO, understand the difference between WebSocket and Socket.IO.

WebSocket is a communication protocol that provides a persistent, bidirectional connection between a client and a server.

Socket.IO is a higher-level library built around Engine.IO that provides event-based communication and additional connection-management features.

Although Socket.IO can use WebSocket as its transport, Socket.IO is not a plain WebSocket implementation. A standard WebSocket client cannot directly communicate with a Socket.IO server.

Feature	WebSocket	Socket.IO
Communication	Bidirectional	Bidirectional
Event names	Application-defined message format	Built-in named events
Automatic reconnection	Must implement	Built-in client support
Rooms	Must implement	Built-in
Broadcasting	Must implement	Built-in
Acknowledgements	Must implement	Built-in
Fallback transport	No built-in fallback	HTTP long-polling
Protocol compatibility	Standard WebSocket	Socket.IO protocol

When should you use WebSocket?

Use the native WebSocket API when you need a lightweight implementation, direct protocol interoperability, and are comfortable implementing reconnection and message management yourself.

When should you use Socket.IO?

Use Socket.IO when you need rooms, broadcasting, event acknowledgements, reconnection handling, and convenient real-time application development.

Remember that Socket.IO adds its own protocol and features, so it cannot be treated as a drop-in replacement for every WebSocket server.