Sounds like you’re almost there 
When starting Natural on the client side, you need to specify an RPC buffer size - RPC=(MAXBUFF=30,RPCSIZE=64) will probably get you going (MAXBUFF is the size of the largest PDA you will send to the server, RPCSIZE is at least 4 greater).
There is a Technical Paper on Servline24 in the EntireX section titled “RPC Tests” that talks about configuring this scenario - Natural to Java RPC server.
Douglas Kelly,
Principal Consultant
Software AG, Inc
#webMethods#EntireX#Mainframe-Integration