And you really should consider switching to TCP/IP due to implementation of RS232 on RFX9600. Also make sure that if you are using Port 3 or Port 4 for connect to Denon that nothing else is on the other port due to Ports 3 and 4 sharing a single UART (as thread below says, search for UART).

Read more about this here:

[Link: remotecentral.com]