SerialParallels 1.0 has been released – this is a new utility to address an area of Parallels that needed it – using serial ports. It’s a free, open-source application, and can be downloaded here.
Description from the website:
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.