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Microsoft RDS 2016/2019 HTML5 Webclient problem

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I have a virtual Netscaler (firmware NS13.0.36.27.nc) for securely publishing my Microsoft RDWEB (Remoteapps & Remotedesktops) to the Internet. It was configured after the best practice documentation and works fine with the old webclient (https://[external name]/RDWeb/Pages), when .rdp files are being downloaded. 


Yesterday I implemented the new HTML5 Client, following these instructions: https://www.tech-coffee.net/deploy-a-windows-server-2019-rds-farm-with-html5-client/

The new client is reachable https://[name]/RDWeb/Webclient and works fine if accessed internally, or if I publish it via NAT over the firewall. It doesen't work when it is being published over Netscaler!


I attached the console error logs from the html5 client. The error message led me to the technet forums, where I found someone with similar symptoms but no solution: https://translate.google.com/translate?sl=auto&tl=en&u=https%3A%2F%2Fsocial.technet.microsoft.com%2FForums%2Fwindowsserver%2Fru-RU%2F96e72f2e-f26f-4057-9835-b414403fe468%2Frds-webclient%3Fforum%3Druwinserver2016


Someone with a nginx reverse proxy also had that problem, that was the solution for him (Source: http://ydtyjku.blogspot.com/2019/06/win-server-2019-rds-html-5-web-client.html):

"I finally figured it out while fixing another issue: the issue was caused by an overly restrictive Content-Security-Policy header added by the nginx reverse proxy.


Before, the header only had default-src; now it has image-src and media-src to allow data: and blob: data types. This is the header that is working currently (probably overly permissive, but it works until we can review it further):


default-src * data: 'unsafe-eval' 'unsafe-inline'; img-src * data: blob:; media-src * data: blob:"


Is there something similar to configure in Netscaler? Somehow allow image-src, media-src and blob data types?


RD Console Logs.txt

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how did you publish your RDWeb HTML5 Portal, via LoadBalancing or Content Switching (if content switching, please check if your expression includes all needed FQDNs or sitepath's)


also what I see in your log is: 


2019-07-11T09:21:20.445Z Core telemetry event: eventName=ConnectionException, traceMessage=An exception has occurred. Details: disconnect code=ConnectionBroken(8), extended code=<null>, reason=WebSocket closed with code: 1006 reason: 
 Thrown in thread 396952 at:


So maybe there is a problem with http websockets, again. Take a look at https://blogs.serioustek.net/post/2014/10/04/load-balancing-remote-desktop-gateway-with-citrix-netscaler-part-2-aspx and check if you enabled websockets at your setup in NetScaler.


Another Option, because of HTML5, could be TLS Versions and Cipher Suites. I would test some older TLS Versions and Cipher Suites with different browsers.




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