Is it possible for the Server that can call GSM/GPRS modules on demand basis

[sb10]

I am working with a project on communication between SIM900 GSM module and a server. Project consist of a client device(enabled with gsm/gprs) and a server system. The client can communicate with server on demand but how can the server communicate to a GSM/GPRS module on demand (since the GSM/GPRS module doesn't have a static but only dynamic ip).
Client can poll the server every-time but its not the method what we are looking for but - the Server should call GSM/GPRS modules on demand basis,
please help me to find a way to do that one.

 

[kgshankar1980]

Then it means your GSM/GPRS module should be in SERVER mode on listening to a port xxxx...

"The server should call GSM/GPRS modules on demand basis" - This is acutally a client..on word sake we always call this as a server software or whatever it is..