Spy on serial port communication

I have the following setup. I have a hardware device connected to COM1 and COM2. In order to test it I have software simulators connected to COM1 and COM2 (RS-232 ports). These simulators receive and transmit data via my hardware device.

I need to calculate the throughput time of my hardware device. For example, if the simulator on COM1 sends a message at time A then I need to establish when it arrives at COM2, giving me Time B. The thro开发者_StackOverflow中文版ughput is then simply B-A.

The problem I'm having is that I can't find a free serial port spy which works accurately enough for my circumstances. I've tried Sysinternals' Portmon, but it is only accurate to a second and I need to know the answer to the nearest tenth of a second. I also tried Free Serial Port Monitor, but it has inaccurate timestamping.

Any suggestions on suitable software?

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Use Portmon. Change the time format; it can show the time in milliseconds (click the timer button on the tool bar - or Ctrl + T or menu Options → Clock Time).

Or use Portmon with more data you can get accurately.