In LXDE:
sudo apt-get update && sudo apt-get install xrdp vino vino-preferences
echo lxsession -s Lubuntu -e LXDE > ~/.xsession
With Unity 3D???
In order to be able to connect to Unity Desktop using xrdp, you will need to have a vnc server that can support recomposing properly your desktop.
To be able to connect to Unity Desktop via xrdp, you will need to follow the following instructions guide : http://c-nergy.be/blog/?p=9962
In summary, You have to
Give it a try
Till next time