Cannot connect to WInXP box with UltraVNC

Peter Coulter peter "at"
Tue Mar 16 21:11:01 2004

Further investigation showed I had all my firewalls (HW and SW) correctly
configured and it really was the work site proxy/firewalls that blocked

So I have followed the SSH/VNC route with success.

All of the following proved useful in this exercise:

Testing remote access to VNC:
Setting WinVNC up SSH:
How to install Open SSH 

When installing Cygwin I encountered a difficulty that some others also had
on WinXP. A solution involving an edit to the Registry (three keys manually
copied from HKCU to HKLM) was suggested. See This was
implemented and worked just fine.

My router is configured to only port-forward port 22 (from external traffic)
to the required SSH server PC (externally sourced 5800 and 5900 traffic is
blocked, internal LAN traffic on these ports is not blocked). The NIS
software firewall running on that PC will only let incoming connections from
a legitimate sub-net. Then running PuTTy and UltraVNC I connected first
time! Good stuff!

Thanks for all help and suggestions received!

Peter Coulter

-----Original Message-----
From: Peter Coulter [mailto:peter "at"] 
Sent: Tuesday, March 09, 2004 8:06 AM
To: 'Scott C. Best'; 'vnc-list "at"'
Subject: RE: Cannot connect to WInXP box with UltraVNC


Inline responses (in a significantly snipped email) ...

> -----Original Message-----
> From: Scott C. Best [mailto:sbest "at"]
> Sent: Tuesday, March 09, 2004 12:24 AM
> To: vnc-list "at"
> Cc: peter "at"
> Subject: Re: Cannot connect to WInXP box with UltraVNC
> ... snip
> > So unless UltraVNC is using some other port(s) I am unaware of then
> > as far as I am concerned NIS is configured correctly (in terms of 
> > ports). Input from anyone on that would be appreciated.
> 	AFAIK, UltraVNC requires only the usual TCP 5900 to work.

As I thought.

> > 2. UltraVNS and NIS 2003 are incompatible
> > I have seen some reports about this and wonder if anyone
> can confirm.
> 	Easy test: does RealVNC (either Viewer or Server) work
> in your setup?

Yes, both Viewer and Server work fine (no probs whatsoever) inside the LAN. 
So I guess that lays the incompatibility issue to rest!
> ... snip
> Have you tried any tunneling of the VNC connection?
> That's a common technique of bypassing the firewall: setup
> your firewalls to work with (say) an SSH connection, then 
> just tunnel VNC through that.
That's my next task (in progress). 

Peter Coulter