already possible with xbmsp/ccxstream, however this has really nothing to do with xbmc, but instead eveything to do with configuring the router/firewall on each side:
Always read the XBMC online-manual, FAQ and search the forum before posting.
Do not e-mail XBMC-Team members directly asking for support. Read/follow the forum rules.
For troubleshooting and bug reporting please make sure you read this first.