*IDOC INBOUND ( NON SAP system ->> SAP system )*

I am transferring IDOC INBOUND ( NON SAP system ->> SAP system ) by calling SAP standard funtc module IDOC_INBOUND_SINGLE using SAP JCo.

In which I am passing all necessary information in Control Record regarding sender and receiver port/IDOC/segment etc.

BUT help me to clarify my doubt that if i am calling a function and i am able to access SAP FM, then why i have to specify the SAP port/RFC connection at RECEIVER end in WE21.

Whats the Significance if i am calling the FM from same SAP system and configuring the port explicitly in WE21.*

If i don't Specify in we02 i am getting error as EDI : RECEIVER PORT in CONTROL RECORD is INVALID