There are a lot of traditional COM port sniffers that is useful tool to intercept RS traffic. Sometimes this is the only way to debug program.
I have been tried to use some of them to intercept VCP for CP2101, but failed (under Windows 2000). May someone recommend me such program that will work with Virtual COM port under Windows 2000/XP
You may try to use the software and sniff your serial port https://www.eltima.com/monitor-com-port/