Websocket error code=500

hi

we get the below

Host: chat.nap
User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:48.0) Gecko/20100101 Firefox/48.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,/;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Sec-WebSocket-Version: 13
Origin: http://chat.nap
Sec-WebSocket-Extensions: permessage-deflate
Sec-WebSocket-Key: bTn6SYJm/GIb0MmQRsgOhw==
Cookie: MMAUTHTOKEN=8ypgar7zi3bkdefrhgwbpxkfta
Connection: keep-alive, Upgrade
Pragma: no-cache
Cache-Control: no-cache
Upgrade: websocket

we have realised that when we go through the url with the port the error has gone away . any ideas what is causing this