If you set up to run over modbus you can do it 
Yes I know about that archaic Modbus Protocol

Maybe I'll go that route unless something better comes along.
It's just I have a simple PIC based I/O controller that costs next to nothing to make (<$10) , has as much I/O as you could wish for and can be programmed in Basic.
Is there any reason in particular that RS232 Rx is not supported?
Wayne....