@EvilDude, there is already a python script for XBMC that can control MediaPortal, (as I understand the only thing that script do not yet support is Live-TV streaming), so maybe you like to start by extending that existing script, see:
MP & XBMC intergration scripts v0.6d Update 4-MAR-07 - MediaPortal Forum
Also
C/C++ interface to TVServer ( potential XBMC client )
The streaming protocol you want to use today is RTSP, ...at least until MediaPortal has a UPnP MediaServer which supports streaming Live-TV over UPnP.
Some related topic-threads in the XBMC forum:
MediaPortal Control Script in the making - XBMC Community Forum XBMC MediaPortal Control Script - XBMC Community Forum New Python Script for MediaPortal Client - XBMC Community Forum
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