This version of the VNC server allows to remote control the real display, e.g. display :0

apt-get install x11vnc

Create the file /home/username/.x11vncrc with the following content:

#x11vnc command line options
# display :0
rfbport 20000
usepw
forever
loop
bg

Create /home/username/.kde/Autostart/startX11vnc:

#!/bin/sh
killall x11vnc &>/dev/null
sleep 10
x11vnc

Make sure it has the correct ownership and permissions:

chown username:username startX11vnc
chmod 750 startX11vnc

Start x11vnc manually the first time to allow for setting up the vnc server password. Afterwards, x11vnc will start on default when kde is starting up.

cd /home/username/.kde/Autostart/startX11vnc
./startX11vnc