[Twisted-Python] Twisted and serial port usage

[Dave Mazzoni]

I'm trying to use a serial port from the twisted library. 
I can get it to show a connection has been made but 
I get no 'dataReeived' calls when I send chars over the serial line. 
I know the serial line is working correctly. 
I think the structure of my program is at fault (of course).

Might anyone suggest the simplest program (for Linux) that 
uses the twisted library? I've got everything else working and love twisted,
but this 'addition' is not working for me.

Thanks,
Dave