The error occurs when a client tries to establish a WebSocket connection, but a network intermediary (like a reverse proxy or load balancer) strips out the required HTTP headers needed to upgrade the connection from standard HTTP to WebSockets .
location /ws { proxy_pass http://your_backend_server; proxy_http_version 1.1; proxy_set_header Upgrade $http_upgrade; proxy_set_header Connection "upgrade"; } Use code with caution. Copied to clipboard 🕸️ Apache Configuration Fix The error occurs when a client tries to
If you are using Nginx as a reverse proxy, you must explicitly tell it to forward the Upgrade and Connection headers. By default, Nginx does not do this. Add or update your location block in your nginx.conf file: proxy_set_header Upgrade $http_upgrade