I did create a little RS232 Interface with level-shifter and two(!) USB-UART converters.
It can be used as RS323-UART-USB in a way that you can
- Forward RS232-data to two USB-clients
- Sniff data between two RS232-devices, RX and TX at the same time.
- Modify during communication (man-in-the-middle)
You can find the files for soldering here: