I’m trying to set up a WebSocket proxy using FastAPI to connect to a Streamlit app, but I’m encountering issues with establishing the WebSocket connection. The Streamlit app is a standard one (not modifiable).

Here’s a simplified version of my FastAPI WebSocket proxy code:

from fastapi import FastAPI, WebSocket, WebSocketDisconnect
import websockets

app = FastAPI()

STREAMLIT_APP_URL = "ws://your_streamlit_app_url"

@app.websocket("/{path:path}")
async def websocket_proxy(websocket: WebSocket, path: str):
    print(f"Proxying WebSocket connection for path: {path}")

    try:
        async with websockets.connect(
            f"{STREAMLIT_APP_URL}/{path}",
            extra_headers=websocket.headers,
            open_timeout=10  # Adjust timeout as needed
        ) as backend_websocket:
            while True:
                try:
                    frontend_msg = await websocket.receive_text()
                    await backend_websocket.send(frontend_msg)

                    backend_msg = await backend_websocket.recv()
                    await websocket.send_text(backend_msg)
                except WebSocketDisconnect:
                    break
                except Exception as e:
                    print(f"Error in WebSocket communication: {e}")
                    break
    except websockets.exceptions.WebSocketException as e:
        print(f"WebSocket connection error: {e}")
        await websocket.close(code=1011)
    except Exception as e:
        print(f"Error connecting to backend WebSocket: {e}")
        await websocket.close(code=1011)

Problem: I’m consistently getting a TimeoutError or WebSocketException when attempting to connect to STREAMLIT_APP_URL. I have verified that the URL is correct and accessible from my server.`

Question: How can I troubleshoot and resolve these WebSocket connection issues between FastAPI and my Streamlit app? Are there specific configurations or best practices I should follow for such WebSocket integrations?

Any insights or suggestions would be greatly appreciated. Thank you!