recently I wrote a small C program utilising the Windows API to communicate with a device over the serial port (COM1, a real serial port of my PC).
This worked fine, but I am aware of the fact that those real COM ports are replaced more and more by USB-to-Serial adapter cables. So I have such a cable here, it's a Prolific USB-to-Serial Comm Port configured to be accessed through COM5.
So I thought since the COM5 should be emulating a real COM device, my program only needs to open COM5 instead of COM1. But I was proved wrong, it did not work. I tried to debug what was happening, but could not find a solution yet. I compared all the COM port's settings (baudrate, flow control, start/stop bits...) but there was no difference between the settings of COM1 and COM5.
What else can be the problem here?