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14 Nov 2018
Glad to announce of release of INDI Library v1.7.5 on 2018-11-14. A few drivers were added in this release as we continue to improve & stabilize existing drivers.
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TOPIC: Cannot launch KStars through VNC

Cannot launch KStars through VNC 2 months 1 week ago #29447

Hello,

I use an Odroid XU4 under Ubuntu 16.04.5 to run KStars (latest release 2.9.8, KDE 5.18.0, Qt 5.5.1). When I launch Kstars from a native display connected to the Linux system, everything works perfectly well (KStars is a beauty on this machine). But when I try to launch KStars through a VNC server, I get the following error (other programs such as PHD2 works perfectly well through VNC):

The X11 connection broke: Unsupported extension used (code 2)
XIO: fatal IO error 22 (Invalid argument) on X server ":1.0"
after 6 requests (6 known processed) with 0 events remaining.
Segmentation fault


The error occurs whatever VNC server I use (TigerVNC, TurboVNC). I tried to use different Window managers (Mate, Xfce4), but it does not change anything, the problem is still here. Going to Ubuntu 18.04 does not solve the problem either. Some googling on the issue did not really help except it might be related to the Qt layer. I am quite frustrated as I really want to be able to use VNC which is quite standard with clients running on many different systems.

Any help on this would be super!

Thanks in advance,
Philippe

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Re:Cannot launch KStars through VNC 2 months 1 week ago #29448

From what I read, this problem might be related to qt5. Did you test with an unencrypted vnc session instead?

-Eric

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HEQ5-Pro - Atik 314E - Orion ED80T - DMK21 on Orion 50mm
DIY 3D-printed Moonlite and FWheel RGB/LPR
KStars and indiserver on two Atom 1.6GHz 1GB RAM Linux, VPN remote access

Re:Cannot launch KStars through VNC 2 months 1 week ago #29452

I tried to disable encryption for the VNC communication and it does not change anything, I get the same error...

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Re:Cannot launch KStars through VNC 2 months 1 week ago #29464

Having unencrypted vnc crashing a x11 ssh tunnel is a bit strange. There should not be any tunnel actually. Could you clarify your setup?

One other test you can do is disregard vnc, open a ssh session with option -X from your client to your odroid, launch kstars from there and compare the results.

-Eric

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HEQ5-Pro - Atik 314E - Orion ED80T - DMK21 on Orion 50mm
DIY 3D-printed Moonlite and FWheel RGB/LPR
KStars and indiserver on two Atom 1.6GHz 1GB RAM Linux, VPN remote access

Re:Cannot launch KStars through VNC 2 months 1 week ago #29465

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.

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Re:Cannot launch KStars through VNC 2 months 1 week ago #29466

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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.

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Re:Cannot launch KStars through VNC 2 months 1 week ago #29467

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

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HEQ5-Pro - Atik 314E - Orion ED80T - DMK21 on Orion 50mm
DIY 3D-printed Moonlite and FWheel RGB/LPR
KStars and indiserver on two Atom 1.6GHz 1GB RAM Linux, VPN remote access

Re:Cannot launch KStars through VNC 2 months 1 week ago #29469

TallFurryMan wrote: 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.

This is Qt 5.5.1. This is a good suggestion, I'll try to install previous version of Qt to see what happens.

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Re:Cannot launch KStars through VNC 2 months 1 week ago #29470

wvreeven wrote: 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.

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.

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Re:Cannot launch KStars through VNC 2 months 1 week ago #29471

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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.

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Cannot launch KStars through VNC 2 months 1 week ago #29472

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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

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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 ?????

Cannot launch KStars through VNC 2 months 1 week ago #29474

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!

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