Myrmidon wrote:
when your on a mobile network you need to use your external ip.

-having a local Ip in your settings will not work outside your own wifi


/Edit:
If u have a dynamic IP, register an account at Dyndns.org and u can use an URl instead of checking your IP all the time.
Theres also a software u can download that checks that the IP doesnt change, or you might have this function in your router aswell