WebSocket Server in Python Not Receiving All Messages While Node.js Does

Question

I am running a WebSocket server behind Nginx, and I have two different implementations: one in Node.js and one in Python. The Node.js WebSocket server receives all messages correctly, but the Python server misses one of the messages.

WebSocket Message Flow:

1. Client opens WebSocket: /my-app/14515/
2. Client sends message: { "type": "my-app:react_api:editor", "url_kwargs": {...} }
3. Client sends message: { "type": "my-app:react_api:problem", "url_kwargs": {...} }
4. Client opens another WebSocket: /editor/14515/

When using Node.js, both messages (my-app:react_api:editor and my-app:react_api:problem) are received. But when using Python, only the first message (my-app:react_api:editor) is logged, and the second one is missing.

---

Nginx Configuration:

location /ws/ {
    proxy_pass http://127.0.0.1:8387/;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
    proxy_redirect off;
    proxy_buffering off;
    proxy_cache off;
    proxy_read_timeout 3600s;
    proxy_send_timeout 3600s;
    include proxy_params;
    proxy_set_header X-Forwarded-Host $server_name;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto $scheme;
}

---

Node.js WebSocket Server (Works Fine)

const WebSocket = require('ws');

const wss = new WebSocket.Server({ port: 8387 });

wss.on('connection', (ws, req) => {
    const clientIP = req.socket.remoteAddress;
    const clientURL = req.url || '/'; 

    console.log(`✅ New connection from ${clientIP}, URL: ${clientURL}`);

    ws.send("👋 Welcome to the WebSocket server!");

    ws.on('message', (message) => {
        console.log(`📩 [${clientURL}] Message from ${clientIP}: ${message}`);
        ws.send(`📢 Echo: ${message}`);
    });

    ws.on('close', (code, reason) => {
        console.log(`🔴 [${clientURL}] Connection closed: Code ${code}, Reason: ${reason}`);
    });

    ws.on('error', (err) => {
        console.error(`❌ [${clientURL}] WebSocket error: ${err.message}`);
    });
});

console.log("🚀 WebSocket server running on ws://localhost:8387");

Python WebSocket Server (Missing Second Message)

import asyncio
import websockets

async def handle_connection(websocket, path):
    client_ip = websocket.remote_address[0]
    client_url = path if path else "/"
    
    print(f"✅ New connection from {client_ip}, URL: {client_url}")
    await websocket.send("👋 Welcome to the WebSocket server!")

    try:
        async for message in websocket:
            print(f"📩 [{client_url}] Message from {client_ip}: {message}")
            await websocket.send(f"📢 Echo: {message}")
    except websockets.exceptions.ConnectionClosed as e:
        print(f"🔴 [{client_url}] Connection closed: Code {e.code}, Reason: {e.reason}")
    except Exception as e:
        print(f"❌ [{client_url}] WebSocket error: {str(e)}")

async def main():
    async with websockets.serve(handle_connection, "localhost", 8387):
        await asyncio.Future()  # Run forever

print("🚀 WebSocket server running on ws://localhost:8387")
asyncio.run(main())

---

Observed Logs

Node.js Logs (Works as Expected)

🚀 WebSocket server running on ws://localhost:8387
✅ New connection from ::ffff:127.0.0.1, URL: /my-app/14515/
✅ New connection from ::ffff:127.0.0.1, URL: /editor/14515/
📩 [/my-app/14515/] Message from ::ffff:127.0.0.1: {"type":"my-app:react_api:editor",...}
📩 [/my-app/14515/] Message from ::ffff:127.0.0.1: {"type":"my-app:react_api:problem",...}

Python Logs (Missing my-app:react_api:problem)

🚀 WebSocket server running on ws://localhost:8387
✅ New connection from 127.0.0.1, URL: /my-app/14515/
📩 [/my-app/14515/] Message from 127.0.0.1: {"type":"my-app:react_api:editor",...}
✅ New connection from 127.0.0.1, URL: /editor/14515/

---

What I’ve Tried So Far

1. ✅ Confirmed the client sends both messages by logging before sending.
2. ✅ Logged path in the Python server to ensure it receives the correct WebSocket connection.
3. ✅ Tried reading messages differently in Python, using:

   while True:
       message = await websocket.recv()
   

4. ✅ Tried adding a small delay (await asyncio.sleep(0.01)) in Python after receiving a message.

---

Question

Why does the Python WebSocket server miss the second message, while the Node.js implementation works fine? How can I ensure Python properly receives and processes all WebSocket messages?