my requirement is RFC 2 FILE synchronus scenario with NW BPM

Hi Experts,

my scenario is RFC 2 FILE synchronus with NW BPM .

Client Requirement :-

BAPI sends the request through SAP PI to B-SYSTEM SFTP server and   after placing the request file in B-system server 240 secs we need to wait for response file so once they place the response file then we need to send the ACKNOWLODGEMENT TO BAPI. and same response file we need to send to another target H- system through SFTP channel.

1st flow- with BPM

         RFC (req)       SFTP           

SAP -------------->PI----------->File-SYS

       <-------------- PI<------------

         RFC(ack)

i am thinking like above scenario  RFC 2 FILE Synchronus with BPM.

what are the design approaches we have in SAP PI  for this requirement please help me on this . This is urgent requirement.

Regards,

Aadi