Virtual Serial Ports Driver (VSPD) creates two pure virtual serial ports in your system which are virtually connected to each other. For other Windows applications, virtual ports will be seen exactly as two real serial ports connected via null-modem cable. You can select any port numbers for virtual pair. For example, you can create virtual pair COM5-COM6. In this case all data sent by other applications to COM5 will arrive at COM6, and all data sent to COM6 will arrive at COM5. This can be seen if you run two HyperTerminals (or any other Windows terminal programs) and connect one of them to COM5 and other one to COM6. Then, all you type in first terminal will appear at second one. Of course, you can transfer files, other data or do whatever you want as it was real serial ports.