WinVNC on Windows 2000 Professional crashes when client connects

James ''Wez'' Weatherall jnw22 "at"
Thu, 14 Jun 2001 14:36:19 +0000

> Note that it is the machine running WinVNC (as a service) which
> crashes (immediate reboot), not the client running VNCviewer.

This means that your Win2K installation has some fundamental low-level
configuration problem, most probably a faulty network or video driver.
Both WinVNC and VNCviewer run at the user level and do not access any OS
structures directly, or install any drivers.  They cannot crash the OS
unless the OS has a bug in it.

Have you tried changing the network card to a different brand, or updating
the drivers?  If the machine is multiprocessor then it's probably just the
case that the network drivers aren't multiprocessor aware.  Another cause
might be use of NT drivers under Win2K, which is a bad idea.

> I suspect that part of the fault may lie in the VNCviewer client,
> as making some seemingly irrelevant changes there often affects
> whether or not the server crashes; I suspect that something that
> the client sends to the WinVNC server causes the latter to crash
> the OS (also, the server tends to crash when the VNC port is scanned
> by security software looking for open TCP ports).#

Nope.  *Anything* the viewer sends to the server is fair game.  If the
server crashes, then that's a bug but it's reasonable.  If the entire server
PC crashes, it strongly suggests a serious bug in the network drivers.

> Connecting from a different client didn't cause the crash.  The
> only difference between the two was that the client which caused
> the server to crash was using a FQDN (specifically, "")
> for the connection to the server, while the client that didn't cause
> the server to crash used a nickname ("bog:0").

Was the VNC server machine also doing DNS?  The above crash sounds like a
timing related problem, which strongly  suggests a serious network driver


James "Wez" Weatherall
          "The path to enlightenment is /usr/bin/enlightenment"
Laboratory for Communications Engineering, Cambridge - Tel : 766513
AT&T Labs Cambridge, UK                              - Tel : 343000
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