WebSocket connection to 'wss://xxxxx/7.1.1-23/doc//c/459/rtl1v/websocket' failed: 

I have a problem .My case is that nignx forwards to another nignx，
nginx->nginx->documentServer.  thank you
WebSocket connection to 'wss://xxxxx/7.1.1-23/doc//c/459/rtl1v/websocket' failed: 

