Usually you get IP info by connecting to some site that echoes your IP address. The bad thing about that method is almost proverbial need of site administrators to make changes to sites or their policies requiring from you to frequently update your code. Another issue could be caching thingy of the Inet approach.
I did some reading about alternative ways to get public IP, and initially tried with SMTP. This Works great but it's kind of slow and on top of that some ISPs tend to block users on p