I will change the logic so that DAVdroid creates UIDs with “_” instead of “@”, and file names according to the UID. This should minimize potential problems.
Probe UDP port and show status when configuring
http://nmap.org/book/man-port-scanning-techniques.html - this page lists technique that allows to probe if a UDP post if closed. It would be awesome to see green button that lights up when you complete IP entry in configuration dialog.