RFC connection to external Interface

Hello,

I want to write a ABAP program that take the use of RFC and gives the output what is there in the flat file.

Suppose in the flat file i have written 'HELLO WORLD' and now this i have to output in sap through writing one ABAP program with the use of RFC .i am not getting how to do it.

WIthout using of RFC i can do it.

But please tell me how to do it as soon as possible .

Thankful.