"An error occurred Connection lost" or "Bad Request the http header is incorrect on Qlik Sense Hub"

Bjorn_Wedbratt — Wed, 10 Feb 2021 10:54:41 GMT

The following errors may be experienced when accessing the Qlik Sense Hub:

An error occurred Connection lost
or
Connection to the Qlik Sense engine failed for unspecified reasons
or
Bad Request the http header is incorrect

Log files may show:

500 Internal error: unable to route websockets request to the following URL, wss://SERVERNAME/PROXY/sense/apps

OR

From Proxy > Trace > Audit:

18 20191107T180810.403-0500 WARN servername Audit.Proxy.Proxy.Core.Connection.Validation.ConnectionDataValidator 25 b3fbafe9-7fba-4cca-8113-587ff923c31e domain\user Http request Host is not allowed: host.fqdn.local 0 c986fb07-a8b8-49c1-9e5c-ac7f56a303a1 ::ffff:127.0.0.1 {header} 21b23e5e635767f3b18a1adbf9f7b62e97100f04

Refreshing the page does not resolve the issue...

An error occurred
Connection lost. Make sure the Qlik Sense is running properly. If your session has timed out due to inactivity, reconnect to Qlik Sense to continue working.

OR

400 Bad Request
The http request header is incorrect

Environment:

Qlik Sense Enterprise, all versions

Cause:

The "Connection lost" error message commonly occurs when:

Qlik Sense Hub is accessed using a different address than the one registered as the default DNS name / Fully Qualified Name of the machine. As an example, when using AWS or similar environments, the internal registered DNS name is not the same as the external facing address
Web sockets are not supported in the environment

Resolution:

This is a general connectivity / websocket related error. It can have a variety of root causes.

I. WebSocket support

Qlik Sense requires WebSockets to be enabled. Third party proxies/reverse proxies or firewalls may not be configured correctly to allow Websocket traffic. Verify if this technology is enabled by navigating to https://websocketstest.com/ from an affected client.

If WebSockets are not available between client and the Qlik Sense server, the Qlik Sense Hub cannot be used.

For directly testing the Qlik Sense server itself, use the Qlik Sense Websocket Connectivity Tester.

II. The address being used when accessing Qlik Sense Hub must be added to the Host White List in the proxy

For detailed instructions, see How to configure the WebSocket origin white list and best practices.

To add an address to the White List, perform the following steps:

In Qlik Management Console, go to CONFIGURE SYSTEM -> Virtual Proxies
Select the proxy and click Edit
Select Advanced in Properties list on the right pane
Scroll to Advanced section in the middle pane
Locate "Host white list"
Click "Add new value" and add the addresses being used when connecting to the Qlik Sense Hub from a client
- IP address: 192.168.0.10
- FQN: myqlikserver.company.com
- (Third party web-portals being used to re-direct users to the Hub)
- etc...
NOTE: An entire domain can be white listed by adding company.com into the white list. This will white list all other addresses within that domain, such as myqlikserver1.company.com, myqlikserver2.company.com, etc.

III. See the following article for additional guidance:

Hub access times out with: Error Connection lost. Make sure that Qlik Sense is running properly