Common VNC Questions and Answers

This is composed largely of ad-hoc extracts from VNC mailing list notes.  It is also almost entirely Windows VNC oriented, due to my focus and knowledge base.  My starting point for information searches on VNC is always the ORL VNC page:

http://www.uk.research.att.com/vnc/intouch.html

You can also sign up for the mailing list from there.

How can I make the VNC server connect to a client, instead of the other way around?

Occasionally it is more convenient to have the server make the connection to a client; if the server has a dynamic IP, this may be the only way to do it.

Here's the process.

Let's say we have a machine at address 192.168.1.1, Client1, which wants to "take over" Server1.
 
(1) Start VncViewer on Client1 with the "-listen" switch, like:

vncviewer -listen

(2) On Server1, make sure that WinVNC is running as a service if possible; it needs to be running already for this to work.  If not, then she just starts it the normal way.  Make sure it's already started before going to Step 3.
 
(3) On Server1 you just run Winvnc with the "-connect" option. If Server1 is typically used only to connect to Client1, you may want to make a shortcut something like this:

"C:\Program Files\ORL\VNC\Winvnc.exe" -connect 192.168.1.1

How to install WinVNC for Windows NT/2000/XP/.NET and through Windows Terminal Services connections

This procedure was developed by Floyd Russell and recently posted by him in the VNC mailing list.  This is the best general method to use when trying to make sure that VNC is installed as a service and ensure that a password is configred both for your sessions and when logging in with no one on console.

If done on a clean install, I have so far always seen this work.

"1. Install VNC
2. Install VNC Service through Start->Programs->VNC->Administrative Tools->Install WinVNC Service
3. Run Start->Programs->VNC->Run WinVNC(AppMode)
4. Enter your password, this is for the current user.
5. Start->Programs->VNC->Administrative Tools->Show Default Settings
6. Enter your password, this is for the local machine
7. Close WinVNC
8. Start WinVNC Service
You may need to start the service helper if you want to modify settings of
the winvnc instance running. This problem is due to the way Terminal
Services operates, since you are working in a virtual desktop."

In my experience, this also seems to be a really good way to make a fussy WinVNC install work on Win2K whether you are installing remotely or not.  Also note that this seems to work well for stable installs on Windows XP.

ORL is closing down! What's going to happen to VNC?

The Olivetti Research Labs facility in Cambridge was closed 2002 April 24 by AT&T, thus ending business at the facility which gave birth to VNC.

Fortunately, the website for VNC has not been shut down, and will continue to be maintained (along with the VNC mailing list) for the foreseeable future.  Since VNC has a large user base including active developers and open source code, this is not nearly the crisis it would be for a closed commercial product.

In fact, it may afford some of the original developers opportunities to pursue more work on VNC.  Here's an extract from a post by Tristan Richardson to the VNC list:

"......the creators of VNC are planning a venture to independently support
and develop VNC as an ongoing open source project. You haven't heard much
from us recently because we've been busy with other projects such as the
Broadband Phone, but now that we have the opportunity :) we're back on the case."

VNC will be re-hosted at Cambridge fairly soon.  Please note that anytime such a move is made there is always some chance of minor outages in service during the switchover; so if the server or list appears to be unavailable for a short period of time at some point, that should be the cause.  It doens't mean someone pulled the plug... :)

How do I suppress the full screen prompt with the Windows VNC Viewer?

There's a registry setting for this - it's covered in the Windows VNCViewer FAQ
(http://www.uk.research.att.com/vnc/winvncviewer.html)
 
Add a DWORD registry value named
HKEY_CURRENT_USER\Software\ORL\VNCviewer\Settings\SkipFullScreenPrompt

and set it to 1.

Why does TightVNC feel slower over a fast Internet connection?

Because you have discovered the tradeoffs between bandwidth consumption and latency.  This was put best by Peter Hutnick in a post to the VNC mailing list:

"...be aware of the difference between bandwidth and latency.  For instance, on a dedicated 100M link VNC "feels" the fastest with "raw" encoding, which uses the /most/ bandwidth.  This is because the server and the viewer don't waste time on encoding/compression to reduce bandwidth use.  [On the other hand], over a slow link the tighter the encoding the faster it feels, because you aren't waiting as much for updates to trickle through the pipe."

 16tX5H-0000BM-00 for vnc-list@uk.research.att.com; Fri, 05 Apr 2002 18:01:07 +0100

Where is the Windows VNC server documentation?

http://www.uk.research.att.com/vnc/winvnc.html

The documentation is very complete.  If you have a question about VNC configuration, it almost certainly is on this page in the section on the Windows VNC registry settings.  Read it carefully: unlike most OEM manuals, this is very compact and precise.  More than once I have found what I thought was a problem or error in the VNC configuration, only to discover on careful reading that it was indeed covered in the VNC documentation.

I've changed the password and can't log on remotely!

This is due to the design compromises VNC had to make to work in a manner structurally identical on Microsoft and Unixish operating systems. The problem is that you have a default password which has not been changed if you changed a user setting.  Here is a post I made to the VNC mailing list on this topic:

The problem is that there are multiple passwords defined in your VNC setup - one for the machine, one for the logged on user.

When you change the password while logged in (when else would you do it, of course) it modifies the password in HKCU, not HKLM.

First, for reference, here is the WinVNC server documentation page.  You've probably already read it, but we'll be referring to a couple of notes in there.

http://www.uk.research.att.com/vnc/winvnc.html

(1) Local/Global Per-User Settings
If you look up Password in the registry settings, you will see that it says it is a "Local or Global per-user setting".
Farther up, you will see the location and a caveat for "Global per-user settings":
 
"Global per-user settings.   These are only read if AllowProperties has not been set to zero[...] Location:
HKEY_CURRENT_USER\Software\ORL\WinVNC3"
 
When you reset your password as a user, this is where you reset it.
 
Now look at the definition for the Local per-user settings:
 
"These override the local default user settings. If there is no current user, the username SYSTEM will be used. Location:
HKEY_LOCAL_MACHINE\Software\ORL\WinVNC3\<username> "
***A note on the above - since you most likely have NOT specifically set a password while logged on as "System", it will look under the username "default" instead. When you first set a password for VNC it appears to set that password for use under "default" also.
 
(2) Export the new password -
Since the password is a REG_BINARY value, you can't reliably copy/paste.  Instead, export it from HKCU\Software\ORL\WinVNC3
 
(3) Import as default:
Simply change the key in the REG file over to
HKEY_LOCAL_MACHINE\Software\ORL\WinVNC3\Default and reimport, and you should be synchronized.

How Do I Clear VNCViewer's List of Recent Connections?

These are stored within the registry under:

HKEY_CURRENT_USER\Software\ORL\VNCviewer\MRU

The following VBScript can be used to automatically clear this out when it is run.

'rmVncMru.vbs
Set oSh = WScript.CreateObject("WScript.Shell")
oSh.RegDelete "HKCU\Software\ORL\VNCviewer\MRU\"

How do I keep VNC from making my Win98 system hang on shutdown?

Tim Pfaltzgraff, one of the regular contributors to the VNC mailing list,, suggests the following as a general fix for this problem.

"Make sure that the following updates are installed:

1) Win98se Shutdown Supplement - MS KB Q239887
2) Win98se Mapped Drives Shutdown Update - MS KB Q260067

Each of these are only 450-505 kb to download, and are harmless if not
needed, but can help greatly if that's what the system needs.  My
desktop system is a Win98se system, and I run the WinVNC server without
shutdown problems."
 

If I run VNCViewer in listen mode, what port does it use?

Luptak Miroslav (HP-Slovakia) has done some experimentation and determined that it appears to use 5500.

How can I use SSH to connect to a listen-only system?

Another procedure posted by Luptak Miroslav:

- execute "vncviewer /listen" on your PC
- on the "server" machine, execute "ssh -L5500:127.0.0.1:5500 your_pc"
- on the "server" machine execute "winvnc -connect 127.0.0.1"