Virtual Serial Port Kit creates virtual serial ports and connects each pair of them via a virtual null-modem cable. So, all the data written to one virtual serial port can be immediately read from the other one, and vice versa.
Moreover, this functionality can be easily integrated into your software.
There are two applications which are exchanging data via serial ports. These programs should be connected and a null-modem cable is used for it.
There are several problems you can come across:
Using Virtual Serial Port Kit you can emulate unlimited number of serial ports and connect each pair of them via a virtual null-modem cable.
So, your applications can exchange data just like they do via hardware serial ports and real null-modem cables.
For example, using VSPK, you can create pair of virtual serial ports (e.g. COM7 and COM8) and connect two applications to them. All data that the first application writes to COM7 is read from COM8 by the second application, and vice versa.
It is easy to test. You can run two copies of terminal program (e.g. standard Windows HyperTerminal) and connect them to COM7 and COM8.
So, all you type in the first HyperTerminal will appear in the second and vice versa. You can also transfer files between HyperTerminals and do whatever you want.

Virtual Serial Port Kit functionality can be easily integrated into your application. So you can create and configure virtual serial ports from your application directly.
Virtual Serial Port Kit is useful for serial software developers.
It allows speeding up development process during debugging and data-logging period. You can debug your program (which uses serial port) by connecting it to another program (e.g. serial device emulator).
You can connect ActiveSync directly to Pocket PC emulator using Virtual Serial Port Kit.