Detecting Loopback correctly

James [Wez] Weatherall jnw "at"
Wed, 08 Jul 1998 10:59:35 +0000

On Tue, 7 Jul 1998, Stephen D. Williams wrote:

> I just ran into a problem where the VNC server (just downloaded) for
> Win95 is refusing connections via localhost.  I can understand wanting
> to prevent loops, however there must be a better way to do this. 
> The reason I ran into this is that we have a demo PC (in a conference
> room with an active white board and overlay projector) that we'd like to
> have usable from anywhere. 
> I setup SSH to forward remote connections (outside the firewall) to
> localhost:5800/5900.  The server complains about not allowing
> connections from loopback. 
> I'm going to try changing it to the specific IP address, but localhost
> is a perfectly reasonable and easiest to maintain way to do this. 

WinVNC checks to see whether an incoming connection has the same IP
address as the machine it is running on and refuses the connection if it
does.  This is mainly to avoid people accidentally viewing a machine's
desktop from that machine and getting weird results.

An option has been added to WinVNC to make local connections possible,
though, in the vnext revision, which will be available soon.


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

The VNC mailing list     -   see