Setting “disable-display-resize” solves the issue for me with UltraVNC. Von: Nick Couchman <[email protected]> Gesendet: Freitag, 24. Oktober 2025 15:36 An: [email protected] Betreff: EXT: Re: Connection to UltraVNC Server
EXTERNAL SENDER Caution: This email originated from outside of Primetals Technologies. Please be cautious when clicking links or opening attachments. Never enter username and password unless having verified the source! On Fri, Oct 24, 2025 at 6:48 AM Timpl, Markus <[email protected]<mailto:[email protected]>> wrote: Hello, I tried to connect to an UltraVNC Server running on Windows 11. The connection works without issue. But there are no screen updates anymore after the initial screen. I am still able to interact with the server to send mouse and keyboard inputs(which I can see with other clients). Other VNC clients are able to connect and get screen updates. I found an old issue describing problems with UltraVNC: https://issues.apache.org/jira/browse/GUACAMOLE-340 I captured the connection between guacd and UltraVNC in Wireshark and can see that UltraVNC sends screen updates to guacd. I can also see that guacd is getting those updates and initiates the rendering process. But it only does the “draft” and “commit” phases, and it doesn’t trigger any of the worker threads. This is very interesting - it actually sounds very similar to an issue that I'm struggling to resolve with RDP + GFX + RemoteApp support: https://issues.apache.org/jira/browse/GUACAMOLE-2123 Your comment, here, that it is doing the draft and commit phases, but not triggering the worker threads, could actually be helpful to resolving both the issue you've identified with UltraVNC and the one I'm struggling with. I'll have to try stepping through that code, again, and see if I can find where triggering the worker thread is being missed. Does anyone have a working connection to an UltraVNC Server? I've not tried UltraVNC, no - most of my current VNC usage has been targeted at TigerVNC. -Nick
