Hi Krishnakant,
Are you trying to call a service hosted on another system? If so, then to be honest, the communication is over HTTP(S), so really you only need to worry about these protocols.
If so you should check out class CL_HTTP_CLIENT.
The SAP help here explains about making a service call.
http://help.sap.com/saphelp_nw70/helpdata/en/1f/93163f9959a808e10000000a114084/frameset.htm
There is also a handy method in this class to create a client by URL.
http://help.sap.com/saphelp_nw74/helpdata/en/b2/86b4512ea4414fb36f17b0568a86ac/content.htm
In order to call the service from your SAP system, you need to check that the ports are open to that paticular host from the SAP system. Your basis guys can check this for you.
I usually run a "telnet" command to the host and port from the calling system as a quick check.
Hope that helps you out.
Cheers,
Katan