For anyone looking to bridge data transfer between Parallels and an RS-232 device, this "SerialClient" program is a great tool. By connecting to a named socket created by Parallels and passing data through a Keyspan USB to serial adapter, it ensures seamless communication with RS-232 devices. Additionally, the ability to log transferred data for protocol analysis is a valuable feature.
You can download SerialClient from:
Please keep in mind that this software is still in beta, so usual disclaimers apply. Happy testing!