I checked it out once it were released. Lately i did not followed up their trace.
Just for this Community i downloaded it now and did following :
Connect through Stealth to a Gameserver
Select 127.0.0.1 as IP and 5005 as Port for AssistUO
Started Assistuo and connected through Stealth on Gameserver.
You need to get following Perspective :
For Stealth , itself is the Client who connect to Gameserver
For other Third Party Software Stealth is the Gameserver ( and located on localhost aka 127.0.0.1 )