How to Use WebSockets: From Python to FastAPI

While building a live options dashboard, a developer discovered that standard HTTP requests couldn't handle the real-time data flows needed for modern applications like chat systems and collaborative tools. WebSocket connections solve this by enabling continuous two-way communication between client and server, unlike traditional HTTP where clients must always request before servers respond. Python's websockets library provides the foundation with methods like websockets.serve() and websockets.connect(), but frameworks like FastAPI streamline development by handling the event loop automatically through Uvicorn. The key difference is that FastAPI requires an explicit await websocket.accept() call, while the plain websockets library accepts connections automatically. WebSockets can transfer both text and binary data, making file transfers possible, and they work with external services using secure wss:// connections. FastAPI's WebSocketDisconnect exception helps handle inevitable client disconnections gracefully, preventing server crashes. Once developers understand asyncio's role in keeping servers alive and remember to explicitly accept connections in FastAPI, building real-time applications becomes straightforward.