I just found a Blackbox 300 Series Server laying around, it's a small RS232 over ethernet server with 8 async ports (RS232C/422/485A).
I have contacted Blackbox, and they will send me a copy of the software which contains setup software and RemoteCOM drivers for Windows.
I'm not sure if I'll use this one for my Domotica system yet. I have 4 com ports available, and no need to extend it too far away from the box. When I have the time for it, I'll try to configure it, and test it.
For those looking for these types of boxes, have a look around for the Blackbox LEF3xx series. More detail can be found in the manual:http://18.104.22.168/manuals/L/LEF31x-USER.pdf