Hi Bhargava,
Please make few checks:
The destination (TCP IP connection) for making this RFC call is working in ECC (SM59). The program ID registered in ECC should be used in the PI RFC sender communication channel and the channel activated.
Check if commit work has been done in the RFC you are using.
Do some dummy changes in RFC adapter and activate it once.
Go through the below link and work with your basis team:
http://howtosap.blogspot.ca/2011/03/create-rfc-tcpip-connection-and.html
seems like a problem with the gateway.
Hope it helps!
Ambrish