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Strange screen saver problem

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bknotts at europa

Mar 2, 1998, 5:31 PM

Post #1 of 4 (1036 views)
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Strange screen saver problem

Anyone seen anything like this?

[bknotts [at] sausag vnc]$ ./vncviewer hostname:0
./vncviewer: VNC server supports protocol version 3.3 (viewer 3.3)
Password:
./vncviewer: VNC authentication succeeded
./vncviewer: Desktop name "HOSTNAME"
./vncviewer: Connected to VNC server, using protocol version 3.3
./vncviewer: VNC server default format:
16 bits per pixel.
Least significant byte first in each pixel.
True colour: max red 31 green 31 blue 31
shift red 10 green 5 blue 0
Using default colormap which is truecolor
Creating window depth 16, visualid 0x20 colormap 0x21
X Error of failed request: BadValue (integer parameter out of range for
operation)
Major opcode of failed request: 1 (X_CreateWindow)
Value in failed request: 0x0
Serial number of failed request: 10
Current serial number in output stream: 12
[bknotts [at] sausag vnc]$

This occurs whenever the Windows NT host is in screen saver mode ("Logon
Screen Saver") or when the logon screen is present. Only the normal
desktop view succeeds in displaying in vncviewer.

Host is Windows NT 4.0, with the normal Win32 host. Guest is Linux
2.0.32 with the normal vncviewer. Window manager is KDE Beta 3.

--
____________________________________________________________________________
Brian J. Knotts e u r o p a c o m m u n i c a t i o
n s
Hostmaster
bknotts [at] europa 503.222.9508 MAIN
http://www.europa.com 503.796.9134 FACSIMILE
503.222.4244 DATA

jnw at orl

Mar 3, 1998, 3:26 AM

Post #2 of 4 (994 views)
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Re: Strange screen saver problem [In reply to]

On Tue, 3 Mar 1998, Brian Knotts wrote:

> This occurs whenever the Windows NT host is in screen saver mode ("Logon
> Screen Saver") or when the logon screen is present. Only the normal
> desktop view succeeds in displaying in vncviewer.

It's a known limitation of WinVNC that it cannot handle non-user desktops.
Desktops are a mechanism used by Windows NT (not Windows 95 or 98) to
isolate tasks that need to be secure, such as the logon shell and
locking/unlocking of workstations. Included in this is the screen-saver.
Unfortunately, this means that since WinVNC runs on the desktop of the
logged-in user, it can't access the logon or screen-saver desktops. The
result is that you attempt to connect to the server and the connection
fails in the manner you describe. To avoid this, WinVNC always tries to
close down the screen-saver if it is running, when a connection is made.

This is partly why it isn't currently possible to use WinVNC to
lock/unlock or logon/logoff NT boxes.

I hope that answers your question.

Cheers,

James "Wez" Weatherall
--
Olivetti & Oracle Research Laboratory, Cambridge, UK.
Tel : Work - 343000

bknotts at europa

Mar 3, 1998, 7:25 AM

Post #3 of 4 (1009 views)
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Re: Strange screen saver problem [In reply to]

-----BEGIN PGP SIGNED MESSAGE-----

On Tue, 3 Mar 1998 10:25:57 +0000 (GMT), James [Wez] Weatherall wrote:

>On Tue, 3 Mar 1998, Brian Knotts wrote:
>
>> This occurs whenever the Windows NT host is in screen saver mode ("Logon
>> Screen Saver") or when the logon screen is present. Only the normal
>> desktop view succeeds in displaying in vncviewer.
>
>It's a known limitation of WinVNC that it cannot handle non-user desktops.
>Desktops are a mechanism used by Windows NT (not Windows 95 or 98) to
>isolate tasks that need to be secure, such as the logon shell and
>locking/unlocking of workstations. Included in this is the screen-saver.
>Unfortunately, this means that since WinVNC runs on the desktop of the
>logged-in user, it can't access the logon or screen-saver desktops. The
>result is that you attempt to connect to the server and the connection
>fails in the manner you describe. To avoid this, WinVNC always tries to
>close down the screen-saver if it is running, when a connection is made.
>
>This is partly why it isn't currently possible to use WinVNC to
>lock/unlock or logon/logoff NT boxes.
>
>I hope that answers your question.

Yes; thanks. I hadn't noticed that before. I guess I'm still a bit confused by VNC's concept of
screens.

I assume it would need to become an NT service for this to be possible, then?

Currently, I've resorted to running the machine headless with no screen saver/lockup. But that's a
little risky. It's nice to be able to have the machine inaccessible from the console.

- --
_______________________________________________________________________________
Brian Knotts http://www.europa.com/~bknotts/ bknotts [at] europa

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jnw at orl

Mar 3, 1998, 7:45 AM

Post #4 of 4 (999 views)
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Re: Strange screen saver problem [In reply to]

On Tue, 3 Mar 1998, Brian Knotts wrote:

[regarding use of lock/unlock or winlogon over VNC]
> I assume it would need to become an NT service for this to be possible, then?

I believe that this would be necessary to get the right priveliges to
access the other desktops, yes. Turning WinVNC into a service isn't
actually difficult but getting the service to handle the different
desktops properly could prove tricky.

> Currently, I've resorted to running the machine headless with no screen saver/
> lockup. But that's a little risky. It's nice to be able to have the
> machine inaccessible from the console.

That's true. ORL has an environment where leaving yourself logged in
tends not to be a problem, since typically anyone who might have sensitive
information on their display has their own office anyway.

We're looking into turning WinVNC into a display driver, which could
potentially solve these sorts of problem. But don't hold your breath!

Cheers,

James "Wez" Weatherall
--
Olivetti & Oracle Research Laboratory, Cambridge, UK.
Tel : Work - 343000

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