I had GPRS enabled sim, and am able to access a remote server (Windows XP) from my mobile. Also, when I connect to the internet, an IP is assigned to my Mobile device. I am not able to access my mobile device using this IP. Moreover I am not able to ping this IP from my remote server. But from My Mobile device I am able to ping the server. I am using Airtel as GPRS service provider. Any idea where the problem lies.
The main aim of my application is two way communication between a Mobile and a Server over internet using some protocol (RMI or http).

Thanks in advance