2 Openhab servers / Homegear address already in use

Hello all,
I have to openhab servers and the moment.
server 1 openhab 2.4 with homegear an the old homematic RF modul
server 2: openhab 3

In addition that I not have a 2, homematic modul I wanted to use the homegear on server1.
First it worked fine and the bridge was detected with the related components.
After few seconds the the things wnt into mode “error” with address already in use
This is clear, the port is already in use on server 1.
The I stoped openhab on server1, but I had the same problem.
So my questions is, how does homegear serve its service. Why the port is already in use if I stopped openhab. Who is using the port og homegear. I have to less knowledge about the data flow from homegear to openhab.

It is possible to have 2 openhab instances on one homegear server.

Is there a better software to simulate the homematic CCU?

I read the related topics to this topic, but I could not found the answer.
Regards Markus