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Cannot launch KStars through VNC

  • Posts: 16
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Thanks for your answer. The setup is really simple, this is what I described above. On the server side: Ordroid XU4, Ubuntu 16.04, a standard VNC server (TightVNC, TigerVNC or TurboVNC). On the client side: any standard client on Windows, Android, ... (tightVNC, VNC Viewer). In all cases and combinations I get the same error, with and without encryption. This error only shows up with KStars and not with any other program used on the Odroid through VNC (PHD2, CCDciel, Siril, ...) - and as I said KStars works perfectly well when launched from the connected display on :0
The VNC server is launched typically with the command "vncserver :1 -geometry 1600x900 -depth 24".
It seems something wrong happens when using KStars / Qt on the X11 display :1
I will try an ssh -X session from an other Linux platform to give it a test.
Thanks again.
5 years 6 months ago #29465

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What happens if you start the VNC server on :0 as well? That's how I use VNC on my Odroid XU4 running Ubuntu MATE 16.04 and have no problems whatsoever. FYI I use vino as VNC server with the RealVNC client over an unencrypted VNC connection.
5 years 6 months ago #29466

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Yes, please disregard my comment about the encrypted vnc session, especially the follow-up I did which is nonsense. My original point was that in my setup, I'm able to use kstars through (unencrypted) vnc, hence my suggestion. But both ends are x86 architectures in my case.

What version of qt are you using on the odroid? From the relatively old QT-45388, it seems rolling back to qt5.4 could be an interesting test. Something related to the presence of the xrandr extension.

-Eric
5 years 6 months ago #29467

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This is Qt 5.5.1. This is a good suggestion, I'll try to install previous version of Qt to see what happens.
5 years 6 months ago #29469

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Thanks for your answer. I am not sure to understand how I can start VNC on 0: since I have an HDMI screen connected to the Odroid XU4 (which locks the :0 display)? Do you mean replicating the same :0 display for the VNC session?
Thanks for the tip about Vinio, I will give it a try.
5 years 6 months ago #29470

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It is possible to start a VNC server on the same display :0 as where the HDMI screen is connected to at the same time. When you then move the mouse, for instance, in the VNC client then you’ll see it move on the HDMI screen as well.
5 years 6 months ago #29471

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Do you have a HDMI monitor attached when you VNC view to the server - if not try it and does it work.

if thats the problem then use of RANDR might help bugreports.qt.io/browse/QTBUG-45624 or use a dummy HDMI plug - need to set the default screen outside of the vnc server for X11.

There is a config file Xorg.conf which might need changing - need to google headless vnc or ask the other user what his file contains as his works :-)

On some Intel machines(x86) with certain graphics cards they dont seem to use xorg.conf
RPI3 Ubuntu 16.04 / AMD desktop Kstars under Ubuntu 16.04 Mounts :azeq6 ,SWAZGoTo

RPI3 Fedora testing out on AMD desktop Fedpra 28 - running kstars 2.9.4 , Indilib 1.7.4 ?????
5 years 6 months ago #29472

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Thanks wvreeven and stach for your answers. I have an HDMI screen connected, and when I launch a VNC server session on it on display :0 rather than :1, it creates some kind of duplicated window manager on it... Then, when I access the Odroid from a VNC client on port 5900, which corresponds to the display :0, I get a black screen.

I saw the bug report Qt uses XRANDR extension without checking and this is what convinced me there is an issue with RANDR. I tried to add 'Option "RANDR" "Enable"' in the Xorg.conf file, but it did not solve the problem. Wvreeven, do you have some specific options in your /etc/X11/Xorg.conf file?

Thanks again!
5 years 6 months ago #29474

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Strange that a second window manager is created. As I said, I use vino and make sure that
- the Odroid user get automatically logged in
- vino is a start up application for the Odroid user
- vino is configured NOT to use encryption

And then I can connect to the same instance as when an HDMI cable is connected. The xorg.conf file I use is
Section "Device"
Identifier      "ODROID"
Driver "armsoc"
Option "Debug"         "false"
Option "DPMS"          "false"
    Option      "NoFlip"    "false"
Option "NoHardwareMouse" "true"
    Option      "NoG2D"     "false"
EndSection
 
Section "ServerLayout"
Identifier      "Default Layout"
Option "BlankTime"     "0"
Option "StandbyTime"   "0"
Option "SuspendTime"   "0"
Option "OffTime"       "0"
EndSection
 
Section "DRI"
Mode            0666
EndSection
 
Section "Screen"
Identifier      "Default Screen"
Device "Mali-Fbdev"
DefaultDepth    24
        SubSection "Display"
            Virtual 1400 1050
        EndSubSection
EndSection

and I don't use xrandr.
Last edit: 5 years 6 months ago by Wouter van Reeven.
5 years 6 months ago #29477

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Thanks wvreeven. I tried Vino, and it works perfectly well, i.e. the screen is replicated on the VNC client (I just needed to disable encryption in Vino as the encryption method is not supported by the traditional VNC clients). However Vino does not work for me since it requires to have a Gnome session opened on a connected screen and I want to be able to use the Odroid headless. This is why in a first place I turned myself to a VNC server that supports XVnc... So I am still stuck at the moment with the X11 error and my best chance might be to downgrade the Qt layer.
5 years 6 months ago #29478

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be careful you haven't got more than one server running or even installed !!!!
I use x11vnc (there are too many to choose from - typical Linux :-) ) headless but with a dummy HDMI else I get a slow screen when no HDMI attached. I start up my Up Core headless wait for the network (ping address until it appears) and then do my VNCviewer from my Laptop/Desktop or whatever (mixture Windows vista,10) - it works

I normally use Realvnc server ,as per RPI, as it works everytime but could not successfully get this to work on the Up Core.

Hope you get sorted with something that works for you - clear skies
RPI3 Ubuntu 16.04 / AMD desktop Kstars under Ubuntu 16.04 Mounts :azeq6 ,SWAZGoTo

RPI3 Fedora testing out on AMD desktop Fedpra 28 - running kstars 2.9.4 , Indilib 1.7.4 ?????
5 years 6 months ago #29480

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Hi everyone
latest kstars from nightly ppa.
Not sure whether this is relevant for the OP's 16.04 but in 18.04, there is screen sharing. I can start kstars from my android tablet; I just grabbed the first vnc app I found in google play. HTH.
5 years 6 months ago #29522
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