SmartCode Web Forum

ViewerX Version 3.5.x crashing on connect/reconnect/disconnect

By CEikeland - 25 Sep 2014


I'm using the ViewerX component a few years now in our products. Every now and then the ViewerX component will crash on connect/reconnect or disconnect from a vnc-server. This will happen with a single VNC-connection or with multiple VNC-connections.

This is reproducible with all the ViewerX versions 3.x.x 

Your ViewerX-Demos are affected and your latest version of VNC-Manger 6.9 is alsow affected. I have send a bugreport on this.

Client OS affected are WinXP, Win7 prof. Win 8 I have not tried yet.

I need this issue fixed!

Hope you can help!!



//Snip Exception Start

24.09.2014 21:18:44: 0000000205: VNC->AxVNCX_Connecting()
24.09.2014 21:18:44: 0000000206: EXCEPTION->ex.MessageEine externe Komponente hat eine Ausnahme ausgelöst. [CLASS:StartApp->HandleUnhandledException][CALLED:SubMain]
24.09.2014 21:18:44: 0000000207: EXCEPTION->ex.InnerException.Message[leer] [CLASS:StartApp->HandleUnhandledException][CALLED:SubMain]
24.09.2014 21:18:44: 0000000208: EXCEPTION->ex.StackTrace   bei System.Windows.Forms.UnsafeNativeMethods.DispatchMessageA(MSG& msg)
   bei System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
   bei System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
   bei System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
   bei System.Windows.Forms.Application.Run(Form mainForm)

// Snip End
By Yury Averkiev (s-code) - 25 Sep 2014

Hi CEikeland,
we have been hunting this bug for close to two years now and frankly, it drives us nuts. No matter what we do we cannot reproduce this crash in a lab. 
Do you see any pattern with those crashes? Any specific details that might help us to reproduce the crash under a debugger? 
By CEikeland - 26 Sep 2014


our test scenario is pretty simple (using the ServerX component):

We set the idleTimeout property of the ServerX component to 10 sec. and let it disconnect.

The ViewerX component will try to reconnect to the ServerX component. And ViewerX will crash!!

Crashes (Exceptions raised!) occure:

- On ServerX disconnect
- On ViewerX connect/reconnect/disconnect
- On reading/setting properties like Viewer.visible etc. no matter what encoding used or scalefactor set.

sometimes it will crash immediately and sometimes it will reconnect fine 20 times until it chrashes.

I hope this will be usefull.


By Yury Averkiev (s-code) - 28 Sep 2014

Would you be able to send us source code of the ViewerX application or debug version of the ViewerX application (we will need pdb files in this case) so we could run it under a debugger?
By CEikeland - 29 Sep 2014


well, you can test it with your own demo-code. Set up the ServerX as mentioned above and let the viewerx client automaticly reconnet to the server.


By Yury Averkiev (s-code) - 8 Oct 2014

We had tried that. My suspicion is that there is a raise condition bug that manifests itself on certain hardware configurations only. We will give it another try, let it run overnight and see if it crashes.
By Yury Averkiev (s-code) - 15 Dec 2014

Hi CEikeland,
we have been able the bug that causes ViewerX and SmartCode VNC Manager to crash upon disconnect/reconnect.

A new build with the fix will be released by the end of this week.
By rick - 17 Feb 2015

Same problem occured when I used ViewerX, so this bug seems no fixed on version 3.5.9.
By Yury Averkiev (s-code) - 17 Feb 2015

Hi Rick,
I'm sorry to hear that. This must be a different bug then. Because since release of the ViewerX 3.5.9 and VNC Manager 6.9.12, we are not seeing disconnect related crashes in the automatic crash reports. 

When ViewerX crashes, what's the memory address where the crash occurs? 
By rick - 3 Mar 2015

Crash Reports :



(same issue I had post on ServerX forum #4644 . )