1)   Bill Serial Port Monitor 3.0L
To monitor (bi-directional) Serial communication RS-232 between two devices without physical cable, you can use the freeware Bill Serial Monitor. This freeware enable you to view, log, test and analyse the activity of the serial RS-232 port.

 2)   Serial Com Port Monitor 4.0
Serial Com Port Monitor was designed for RS232/422/485 COM ports monitoring. It monitors, displays, logs and analyzes all serial port activity in a system and solves problems of debugging computer connection with peripheral devices using COM port.