👀 Views: 28 💬 Answers: 1 📅 Created: 2025-08-21

nginx flask websockets Python

I'm trying to implement I've hit a wall trying to I've been banging my head against this for hours..... I'm having trouble with my Nginx reverse proxy setup for a Flask application running on Ubuntu 20.04. The WebSocket connections are failing, and in the Nginx behavior logs, I see messages like `upstream prematurely closed connection while reading response header from upstream`. I have configured my Flask app to accept WebSocket connections using Flask-SocketIO and I'm using the eventlet server. Here's a snippet of my Nginx configuration: ```nginx server { listen 80; server_name myapp.com; location / { proxy_pass http://localhost:5000; proxy_http_version 1.1; proxy_set_header Upgrade $http_upgrade; proxy_set_header Connection "upgrade"; proxy_set_header Host $host; 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; } } ``` I've tried modifying the `proxy_pass` configuration and ensuring that both the Nginx and Flask applications are running, but the WebSocket connections still do not initiate properly. Also, my Flask app is running the following: ```python from flask import Flask from flask_socketio import SocketIO app = Flask(__name__) socketio = SocketIO(app) @socketio.on('message') def handle_message(data): print('Received message: ' + data) if __name__ == '__main__': socketio.run(app) ``` When I try to connect to the WebSocket from the frontend, I see the behavior `WebSocket connection to 'ws://myapp.com/socket.io/?EIO=3&transport=websocket' failed:` in the browser console. I’ve also verified that the ports are open and accessible. Any insights on what might be causing this scenario or how to properly configure Nginx to work with WebSockets in this scenario? I'm working on a service that needs to handle this. I appreciate any insights!