Hi Dipesh,
I recommend to use the SAP Business Connector: https://service.sap.com/sbc-download
After installation and setup you can already send IDocs from the SAP System to the SBC, which then converts it automatically to IDoc-XML format and makes a PUT to an FTP server.
(In the SAP BC SapAdapter Guide see the chapter about "Routing IDocs and XML messages", as well as the section about the "FTP Outbound Process" in the chapter "The Partner Manager".)
Best Regards, Ulrich