How to get Internet IP address?
Try searching in the offline help. Searching for "ip address" will lead you to a few choices, one of which is the command: ssCore.SysInfo.getIPAddress.
That will get you the IP address of the computer the program is running on. That doesn't mean it's the address servers see. If the computer is on a network then the computer's Internet connection is most-likely going through a router or server that has a different IP address facing the outside world.
that beeing said, the only somewhat reliable way is to query your own server via LoadVars and let him answer with the IP the request came from.