Hi deloptes:
I have a virtual machine running OwnCloud. Calender and addresss data is
managed on the computer with thunderbird (or by the web frondend) and
for syncing there are cheap (~ 1€) apps for iphone and adroid and windows.
There is a file syncing tool in debian available, but I use konquerer
with webdav to access files.
I found no way to use CalDav and/or CardDAV with net connections (only
on local machine) and get no answer for related question on this list.
Hope that helps
Rolf