Knowledge

[Lisa_Sun]

This article covers how to begin troubleshooting connectivity issues in Qlik Sense if the WebSocket connections are suspected.

Qlik Sense uses WebSocket to communicate the client requests from the web browser to the Qlik Sense engine/server.  Devices or software used between client and engine therefore need to support WebSocket technology, such as firewalls, reverse proxies, load balancers, network policies, hardware devices, etc. For more information about WebSockets see WebSocket (Wikipedia).

A great first step to begin verifying if WebSockets are enabled is to test your browser: How To Check If The Browser Works With WebSockets 

This verifies browsers, however if the issue is present on the network layer between the devices, our WebSocket connectivity Tester can help identify this: Qlik Sense Websocket Connectivity Tester. 

Should WebSocket connectivity drop due to timeouts when idling, see Enabling TCP Keep Alive Functionality In Qlik Sense.

If WebSockets cannot be established at all, please see the video posted under Hub access times out with: Error Connection lost. Make sure that Qlik Sense is running properly. 

If further guidance is need please engage your network administrator and network vendor for further troubleshooting. Qlik Support cannot assist in configuring individual network equipment or software. 

Related Content/Examples:  

We have compiled a list of links that can provide initial ideas on how to proceed with enabling WebSockets reliably. 

1.  Example to turn on web socket on load balancer.
   
   https://www.nginx.com/blog/websocket-nginx/
   https://github.com/facebookincubator/create-react-app/issues/2260
   
   
2. Example to turn on web socket on Amazon Elastic Load Balancer (ELB)
   
   https://campus.barracuda.com/product/webapplicationfirewall/doc/49054741/how-to-enable-websocket/
   
   
3. Example to turn on web socket on IE
   
   https://msdn.microsoft.com/library/ee330736(v=vs.85).aspx#websocket_closetimeout
   
   
4. Example to turn on web socket on Chrome
   
   https://www.quora.com/How-do-you-enable-WebSockets-in-Google-Chrome
   
   
5. Web Browser versions that support web socket
   
   https://caniuse.com/#search=websocket
   
   
   
6. Hub access times out with: Error Connection lost. Make sure that Qlik Sense is running properly