Parallels only supports serial ports as sockets on the host OS. SerialParallels connects to such a socket and binds it to a real serial port. To use it, add a serial port as a server socket on the virtual machine. Start the virtual machine then run SerialParallels. Set its socket type to client and select the file to match that in Parallels. Set the serial device and associated settings then hit the enable button.
GERBILBOX It's not the simplest thing to use in the world, but then again this is about interfacing with Windows (under Parallels). It required that I fiddle with the settings, but this little program allowed Windows to recognize a serial-based Garmin 76S GPS via a Keyspan serial-to-USB converter. (Version 1.0)
PETER DA SILVA Oh man, if you could only do that for USB PalmOS devices... so I could connect my PDA to Palm Desktop under Parallels. I've been burned too many times by i"Sync" to trust any of the iSync conduits for iCal/Address Book/...
Currently I'm making do with syncing my Clie to my Mac Mini. (Version 1.0)