Hi
I am fighting with IDOC connection (Jco) since the last weeks and I think I have now understood how it really works with AEX and Jco connections.
In general it is not the best interface design to use old Jco technology to connect to a non-ABAP system like AEX!
Jco is an API for ABAP stack, and so the NON-SAP system should change their interface to SOAP or …
But we all know that it is not easy to tell them that.
Who will pay, the project was a PI migration with little budget. 
The software supplier will always say that his SAP connection is certified and so AEX is a SAP product and has to accept this
On Idoc level I found several ways to do this successful but it is not what I like.
Maybe my input can help to solve the RFC issue as well.
I have currently no RFC Jco server but I configured my PI Sender RFC channel and got a green status.
But as I wrote it is not the future to connect old Jco solutions with AEX.
Please try this setup and give feedback if this solve your problem.
One more hint: Please use PO gateway also for IDOC communication and not SAP ERP gateway.
I love smgw but SAP told me that the future is to use the PO gateway and after my research in the last weeks I agree with SAP.
