WebSocket Handshake: Unexpected Response Code: 404 – Troubleshooting Guide

Error Overview

The error message “WebSocket handshake: Unexpected response code: 404” indicates that a WebSocket connection attempt has failed due to a 404 Not Found response from the server. This typically means that the requested WebSocket endpoint does not exist or is incorrectly configured. Identifying the root cause is crucial to restoring proper WebSocket functionality.

Common Causes

Several factors can lead to the “WebSocket handshake: Unexpected response code: 404” error:

1. Incorrect WebSocket URL: The URL used to initiate the WebSocket connection might be incorrect or malformed.
2. Server Misconfiguration: The server may not be correctly set up to handle WebSocket requests, particularly if a proxy server (like Nginx) is involved.
3. Firewall or Security Settings: Security measures on the server or network may be blocking WebSocket connections.
4. Outdated Libraries: Using outdated libraries or dependencies can lead to compatibility issues.
5. Protocol Mismatch: The server may require a specific protocol that is not being used in the connection attempt.

Solution Methods

To resolve the “WebSocket handshake: Unexpected response code: 404” issue, follow these methods:

Method 1: Reinstall Tornado

Many users have resolved this issue by reinstalling the Tornado library, particularly downgrading to a compatible version.

1. Open your terminal.
2. Uninstall the current Tornado version:
   bash
sudo pip3 uninstall tornado
3. Install a specific version of Tornado:
   bash
sudo pip3 install tornado==5.1.1
4. Verify that the installation was successful.

This method has solved the issue for many users experiencing similar problems. Source

Method 2: Check WebSocket URL

Ensure that the WebSocket URL is correctly formatted and points to the correct endpoint. A common format is:

ws://yourdomain.com/path/to/socket

• Make sure the path matches what is configured on the server.
• If you are using a secured connection, change ws:// to wss://.

Method 3: Configure Nginx for WebSocket Support

If you are using Nginx as a reverse proxy, ensure that it is properly configured to support WebSocket connections. Add the following lines to your Nginx configuration file:

“`nginx
location /your-websocket-endpoint