Using xhost with Ubuntu/Kubuntu Linux running gdm or kdm

I was just chatting to a work colleague about the ease and wonders of X11 as part of extolling the virtues of the Linux Terminal Server Project, when I said I'd show him how it works.

So I tried to do 'xhost +' on his machine and then ran xeyes from my machine giving his machine's IP address in the -display option, but it didn't work! Trawling the web, I found that Ubuntu had tightened things up:

http://davesource.com/Solutions/20070912.Ubuntu-xhost.html

This solution works for gdm users, but my colleague and I both run kdm (kde4) to control acces to X. So here's the expanded instructions:

1. Edit /etc/X11/xinit/xserverrc:
   Remove (or comment out) the "-nolisten tcp"
2. Edit /etc/X11/kde4/kdm/kdmrc:
   Find the line 'ServerArgsLocal = -br -nolisten tcp and comment out the '-nolisten tcp' bit.
3. Log out of X (GNOME or KDE) and log back in again (this should restart the kdm or gdm process).

Having done that it should work thus:

My machine's IP is 192.168.0.10 and my colleagues is 192.168.0.20. On my colleague's machine, having done the above he opens a command line and issues:

% xhost +
% xeyes -display 192.168.0.20:0.0

And xeyes appears on his screen!