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Embedded VNC and Mate environment: Stuck on the first connection if screen is locked

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i have a very strange behavior when connecting to an Ubuntu 18.04 server with Mate environment and TigerVNC server 1.9.0 installed, if i have the remote desktop locked (ubuntu mate use mate-screensaver for screen locking).

I will try to explain this strange behavior at the best:

- If i leave the remote desktop unlocked, i don't have any problem, when i open the VNC session i can see immediately the remote desktop;
- If i have the remote desktop locked, when i open the VNC session i can't see immediately the login form, but the embedded VNC client get stuck on a blank screen that came before the login screen; at this point if i reconnect the embedded VNC client (for example using the reconnect button that appears with the right click on the session tab) the login form appear.

So when i connect to this remote session with screen locked i'm expecting to automatically see the login form, that is:


instead the vnc connection get stucked on this screen that came before the login screen:


when the connection is stuck on the second image, if if disconnect and the reconnect the embedded VNC viewer then I can see the login form.

Also these behaviors occur:

- when the connection is stuck on the second image, if i press some key, then disconnect and reconnect the viewer i can see that these keys appear in the password form;
- when i'm in the login screen, if i click the cancel button the login screen disappear, and the connection get stucked again on the second screen. The normal behavior should be that the login screen appears again;
- when i'm in the login screen, if i disconnect and then wait a sufficient amount of time (Mate timeout for insert password i think), on the next connection the embedded VNC viewer get stuck again on the second image.

I think that the connection to the server is not completely stuck but the embedded VNC client doesn't update the image any more after showing that blank screen.

None of the above problems appear with others VNC client; i tested:

- Android version of RDM;
- UltraVNC;
- TigerVNC viewer.

On another server, where i have installed Ubuntu 16.04 with LXDE environment and TigerVNC server 1.9.0, i don't have this problem with the embedded VNC viewer if the screen is locked (LXDE use xscreensaver for screen locking).


Clock8 mths


I had a chat with one of our developer and he will try to reproduce your issue internaly, but it could be difficult to reproduce.

On a side note, could you confirm that Native UltraVNC and Native TigerVNC Viewer encountered the issue as well?
If yes, then, we could suspect an issue with the TigerVNC server.

Best regards,

Jeff Dagenais

Clock8 mths


unfortunately the issue occur only with the windows version of RDM, using the embedded VNC viewer.

Any other VNC client, including the android version of RDM, doesn't show this problem.


Clock8 mths


I tried to replicate this issue but so far i've been unsuccessful.

My test setup.
Ubuntu 18.04 running MATE.
tigervnc 1.9 started with x0vncserver

Is there anything else I should have done to match your setup?

Jonathan Lafontaine


Clock8 mths


my server is an headless one, so i need to use a virtual screen which is provided by the vncserver command. The x0vncserver is used to share and existing X server, like the one created by a physical screen.

I have:

-Ubuntu 18.04 64bit with MATE, upgraded to 18.04.2 without installing the Cosmic HWE stack
-tigervnc 1.9.0+dfsg-1 installed with the deb file of ubuntu 18.10 ( tigervnc-common, tigervnc-standalone-server, tigervnc-xorg-extension.
-tigervnc started with: vncserver -depth 24 -geometry 1920x1080 -X509Cert /etc/letsencrypt/live/HOSTNAME/cert.pem -X509Key /etc/letsencrypt/live/HOSTNAME/privkey.pem -SecurityTypes X509Vnc :1 +extension COMPOSITE

I have this problem even without X509 encryption (standard VncAuth SecurityTypes) and without the +extension COMPOSITE

Clock8 mths