4.4.2 - Downgrade options? CRASHES Master and Clients, No Demo

  • @tobydox

    BSOD death seems to have been resolved. I updated to 4.5.2 a couple of days before we left for Christmas, and I have not seen 1 BSOD in the last ~5 school days...and I was getting 1-2 per class period.

    But unfortunately, STILL NO DEMO.

    Is anybody else experiencing No Demo? When I click the option, it does go to Demo, but it either just stalls for a long time and/or eventually displays an old image long before the current students even logged in. I am still trying to track down exactly what , and from where/when, DEMO is pulling the display view.

  • @drewloker

    Do you have 4.5.2 installed on the student computers?

  • @itguy Yes, 4.5.2 is on Master and all clients.

    Any other ideas on why Demo is not working? Otherwise, 4.5.2 is running stable.


  • @drewloker

    Not really, a lot variables in play.

    Possibly VLAN QoS, network interface drivers, even anti-malware scanning.

    I haven't experienced this particular issue.

  • 4.5.2 with 25 client.

    Sometime demo work fine, sometimes it doesnt , i wonder whats wrong , and ill give up now, they said 4.5.2 is stable , but demo it a bit pain.

  • @itguy
    Thanks for trying.

    I just don't understand why it will work if I take the lab back down to 4.3.

    • 4.3 - Demo worked perfect.
    • 4.4.2 - It worked if nobody was in the room, but 4.4.2 was unstable. And, once a class came in, and more than a couple of students were logged in, Demo failed to work...showed an image from some other time period.
    • 4.5.2 - is stable, but Demo will not working at all, even if I am only testing with one student logged in.

  • We'll have a look at the demo issue and try to resolve it in 4.5.3. Veyon 4.5 comes with a rewritten implementation demo feature so it's likely there are still some bugs due to the big changes.

  • @tobydox

    OK!! I finally have a new clue!

    EDIT: Sometimes! I wrote the following...but then signed into two more clients, and now NOTHING is working again, not even on the one I had tested and resolve the following. ARGH!!!!

    What I THOUGHT was progress...
    If I select "All screens", Demo works, but only shows Display2). The problem is I don't really want Display 2 to go to the Clients. Display 3 is what is going to the TV monitors in the room (via HDMI splitter) and I would really like for what they see on the screen to be the same as what I display to the entire class.

    Also, Clients only receive some of my Display to their monitor...resolution differences...but this anomaly has been with Veyon for 3 years...so this is to be expected.

    If I select Screen 1 [\.\Display2], it works. No difference as above as to the amount that goes to the clients.

    If I select Screen 2 [\.\Display3], Demo does NOT work. Just sits there hanging o n "Connecting". Black screen on client until I stop Demo.

    If I select Screen 3 [\.\Display4], Demo does not work...same as above.

    I don't even know what Display 4 is as i have three Display using Built-in Video on VGA, Display Port and HDMI out all working together for 3 monitors.

    But, this work before on 4.3, just stopped working on 4.4.2. A version after 4.4.2, maybe 4.5?, brought in the option to select a screen/display. That version didn't work for crashing, nor Demo. Maybe right before you all added the option to select the screen, the coding was added that broke the Demo. ??? (just spit balling there).

    So, 4.5.2 is stable. And I have now determined that some of the options in Demo work.

    Demo options Veyon.JPG
    display settings with 3 monitors.JPG

  • Thanks for figuring out! So it seems to be related to a non-standard arrangement of screens. I'll test this and if necessary provide a bugfix 🙂

  • @drewloker

    My understanding is \\.\DISPLAY2, \\.\DISPLAY3 and \\.\DISPLAY4 are device names representing display output or screens.

    In Clone mode screens and monitors could pair as;


    where one screen is applied to two logical monitor devices.

    In Extended mode screens and monitors could pair as;


    where two screens are applied to one logical monitor device.

    You can think of \\.\DISPLAY1 and \\.\DISPLAY2 as the output of the graphics card drivers/interface (screens) while \\.\DISPLAY1\Monitor0 and \\.\DISPLAY1\Monitor1 represent the attached monitors.

    Two Nirsoft utilities, ControlMyMonitor and MultiMonitorTool, provide screen, monitor and adapter information with both GUI and command line control.




    Extract both using the 7-Zip utility, https://www.7-zip.org/download.html, and for convenience place the extracted files into the C:\Windows folder.

    Command line:
    C:\Windows\MultiMonitorTool.exe /stext "C:\Users\Public\Desktop\monitorinfo.txt"

    C:\Windows\ControlMyMonitor.exe /smonitors "C:\Users\Public\Desktop\monitorinfo2.txt"

    Question: Do any of the three monitors have touchscreens?

  • I’m not familiar with Veyon throughput or whether this is configurable. Generally I haven’t experienced performance issues using either Fullscreen demo or Window demo and though deselecting unused computers would achieve a modest performance gain my experience has been this doesn’t work very well on the fly. Since you are down to two lists I think it would be best to exit and restart Veyon whenever your selections change.