If so, then go with named pipes and problem solved
The config folder thing is of course off-topic, but you should consider reviewing your setup -- Windows' version, the last time I checked, also made a .rainlendar2 in the User folder, which probably is OK for Vista, but under XP appdata should go into %APPDATA% which usually resides in "User\Application Data". A simple thing to fix. Also the dot is ugly for Windows.
The Linux thing is also easy to fix, but means a lot, because regular Unix/Linux users don't expect to find hidden folders inside a hidden folder -- the Filesystem Hierarchy Standard also states that. Just do a check of ~/.rainlendar2 and ~/.config/rainlendar2.
Read a bit on standard usage on both OSes, because the hybrid of both looks tacky.