Error analysis
websocket: the client is not using the websocket protocol: 'upgrade' token not found in 'Connection' head
WebSocket
This problem occurs when the reverse proxy or load balancer is not delivering the request correctly.
solution
Nginx plus the following analysis
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection upgrade
Apache plus the following analysis
<Location /ws>
ProxyPass ws://localhost:8000
ProxyPassReverse ws://localhost:8000/
</Location>