Backend & APIs · Intermediate
Real-Time Chat with WebSockets
Build a WebSocket chat server and client supporting multiple rooms, presence and typing indicators, and live message broadcast to all connected members.
You build a real-time chat application where clients connect over WebSockets and exchange messages instantly without polling. The server manages connections, groups them into rooms, broadcasts each message to everyone in the room, and tracks who is online and who is currently typing. The client opens a persistent socket, renders incoming messages live, and sends presence and typing events. It is worth building because real-time bidirectional communication underpins chat, collaborative editing, dashboards, and multiplayer features, and it makes you handle connection lifecycle, broadcast fan-out, and reconnection. It is resume-worthy because it proves you understand stateful connections and event-driven server design, which differ sharply from request/response REST work.
What you build
- Persistent WebSocket connections with a clean handshake and close handling
- Multiple named rooms users can join and leave
- Message broadcast to all members of a room
- Presence tracking showing who is currently online
- Typing indicators pushed in real time
- Reconnect logic with message backfill on rejoin
- Username assignment and basic join/leave system messages
What it teaches
- WebSocket lifecycle and the upgrade handshake
- Event-driven, stateful connection management
- Broadcast fan-out and room-based routing
- Presence and ephemeral state modeling
- Client-side reconnection and backfill
- Differences between push and request/response architectures
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Take it further
- Persist message history to a database and load it on join.
- Scale across instances with a Redis pub/sub backplane.
- Add authentication so usernames map to real accounts.
