#bidirectional

Enable real-time features with Socket.io. Implementation: 1. Server-side io instance. 2. Client-side connection. 3. Emit and on for events. 4. Rooms for group messaging. 5. Broadcasting to multiple clients. 6. Acknowledgements for reliability. 7. Middleware for authentication. 8. Automatic reconnection. Use with Redis adapter for scaling across servers and implement presence detection.

Implement WebSocket for real-time features. Use cases: 1. Chat applications. 2. Live notifications. 3. Collaborative editing. 4. Live data dashboards. 5. Gaming multiplayer. 6. Stock tickers. Implementation: Establish connection, send/receive messages, handle disconnect, reconnect logic, heartbeat/ping-pong, scale with Redis pub/sub, authentication at connection. Use Socket.io or native WebSocket API.