Thanks a lot!

After the first problems with network latency (some characters were received in the wrong order) I added a first in-first out stack for the sender and for the receiver module. I will try to add to the communication a response channel if a keycode is sucessfully received or not. But I wan't to use only a single port. Don't know if this could work. I wan't to keep the settings as simple as possible.
If there occurs problems with some fast typers I could bundle some keycodes together in a single packet to minimize the overhead. Currently every keycode is sent seperate. If you type to fast your text appears a little bit delayed. But perhaps this is because of the way I send the keycodes to different applications at the N900.

This creates currently by biggest headache. At MeeGo exists the virtual Keyboard plugin maliit - I will use it for the MeeGo releases end expect less problems.
But at maemo I haven't found something similar to this. I'm currently using the command line tool xdotool to send the keycodes and created manually a table to translate at the N900 the received keycodes in keystrikes.
Have a look at this thread: Best way to send keycodes - emulate keyboard press

It's a pain and feels unprofessional. Any kind of suggestions are welcome!