Build a WebSocket Server

Build a WebSocket server for real-time communication.

Requirements:
- Framework: [NODE.JS WITH WS / SOCKET.IO / FASTIFY / etc.]
- Use case: [CHAT / LIVE NOTIFICATIONS / REAL-TIME DASHBOARD / COLLABORATIVE EDITING]
- Authentication: [JWT / SESSION / NONE]
- Expected concurrent connections: [APPROX]
- Persistence needed: [REDIS FOR PUB/SUB / IN-MEMORY / DATABASE]

Provide:
1. Server setup with connection handling
2. Event structure (how messages are typed and dispatched)
3. Authentication/authorisation middleware
4. Room or channel management (if applicable)
5. Reconnection handling on the client side
6. Basic client-side example to connect and send/receive messages
7. Scaling considerations (what to change when going beyond a single server)