Ultimate Guide to Building a WebSocket Server in Python (2025)

Introduction to WebSocket Server in Python

Understanding the WebSocket Protocol

• Persistent connection (no repeated handshakes)
• Lower overhead for continuous data exchange
• Bidirectional messaging

WebSocket Handshake Lifecycle

Choosing the Right WebSocket Server Library in Python

• websocket-server: Quick setup for simple projects, supports SSL.
• websockets: Fully asynchronous, ideal for high concurrency and modern Python (asyncio).
• SimpleWebSocketServer: Minimal dependencies, easy for demos or education, but lacks SSL support.

Setting Up Your First WebSocket Server in Python

Step 1: Installing Dependencies

1pip install websocket-server
2pip install websockets
3pip install SimpleWebSocketServer
4

Step 2: Writing a Basic WebSocket Server (websockets library)

1import asyncio
2import websockets
3
4async def echo(websocket, path):
5    async for message in websocket:
6        await websocket.send(f"Echo: {message}")
7
8start_server = websockets.serve(echo, "localhost", 8765)
9
10asyncio.get_event_loop().run_until_complete(start_server)
11asyncio.get_event_loop().run_forever()
12

Step 3: Connecting a WebSocket Client

1import asyncio
2import websockets
3
4async def hello():
5    uri = "ws://localhost:8765"
6    async with websockets.connect(uri) as websocket:
7        await websocket.send("Hello, server!")
8        response = await websocket.recv()
9        print(f"Server says: {response}")
10
11asyncio.run(hello())
12

1const ws = new WebSocket("ws://localhost:8765");
2ws.onmessage = (event) => console.log(event.data);
3ws.onopen = () => ws.send("Hello from browser!");
4

Step 4: Testing Your WebSocket Server

Advanced Features for Python WebSocket Servers

Handling Multiple Clients (Broadcasting)

1import asyncio
2import websockets
3
4connected = set()
5
6async def handler(websocket, path):
7    connected.add(websocket)
8    try:
9        async for message in websocket:
10            await asyncio.gather(*(ws.send(f"Broadcast: {message}") for ws in connected))
11    finally:
12        connected.remove(websocket)
13
14start_server = websockets.serve(handler, "localhost", 8765)
15
16asyncio.get_event_loop().run_until_complete(start_server)
17asyncio.get_event_loop().run_forever()
18

Asynchronous Programming with asyncio

1import asyncio
2import websockets
3
4async def time(websocket, path):
5    while True:
6        await websocket.send("The time is: " + str(asyncio.get_event_loop().time()))
7        await asyncio.sleep(1)
8
9start_server = websockets.serve(time, "localhost", 8765)
10
11asyncio.get_event_loop().run_until_complete(start_server)
12asyncio.get_event_loop().run_forever()
13

Adding SSL/TLS for Secure WebSocket Server Python (wss)

1import asyncio
2import ssl
3import websockets
4
5ssl_context = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
6ssl_context.load_cert_chain(certfile="cert.pem", keyfile="key.pem")
7
8async def echo(websocket, path):
9    async for message in websocket:
10        await websocket.send(message)
11
12start_server = websockets.serve(
13    echo, "localhost", 8765, ssl=ssl_context
14)
15
16asyncio.get_event_loop().run_until_complete(start_server)
17asyncio.get_event_loop().run_forever()
18

• Always use strong certificates (not self-signed in production)
• Validate origins if exposed to browsers
• Keep dependencies updated

Error Handling and Logging

1import logging
2logging.basicConfig(level=logging.INFO)
3
4try:
5    ... # server code
6except Exception as e:
7    logging.error(f"Server error: {e}")
8

Real-World Use Cases for WebSocket Server in Python

• Chat applications: Real-time messaging between users.
• Dashboards and monitoring: Instant updates for data visualization or admin panels.
• Multiplayer games: Low-latency state sync between players/servers.
• IoT and device communication: Efficiently stream sensor data or send device commands.
• Collaborative tools: Shared document editing, whiteboards, or code editors.

Performance, Scalability, and Deployment Considerations for WebSocket Server Python

• Concurrency: Use asyncio or libraries like websockets to handle thousands of clients.
• Scalability: Distribute load across multiple processes (using multiprocessing, uvicorn, or gunicorn for ASGI apps).
• Deployment: Containerize with Docker, and deploy on cloud platforms (AWS, Azure, GCP) for auto-scaling.
• Supervision: Use supervisor or systemd to ensure your websocket server python process restarts on failure.

Deployment Flow Diagram

• Use gunicorn or uvicorn for ASGI-based websocket servers.
• Set resource limits and monitor connection count.
• Load test your websocket server python before production.

Common Pitfalls and Troubleshooting Tips for WebSocket Server Python

• Firewall and port issues: Ensure your server port (e.g., 8765) is open to clients.
• Browser compatibility: Use modern browsers supporting WebSocket; check protocol (ws:// vs wss://).
• Handshake failures: Check server logs for SSL or CORS errors; validate client and server are on the same protocol and host.

Conclusion: Next Steps with Python WebSocket Servers

References & Further Reading

• WebSocket Protocol RFC 6455

• websockets Python library

• Python asyncio documentation

• Real-Time Web Apps with WebSockets