Before starting off with this tutorial, let's get on with a little bit of background on serial communication, null modems, and virtual ports.
A serial port (COM port) is an asynchronous port on the computer used to connect a serial device and capable of transmitting data one bit at a time or serially. Most serial ports on computers conform to the RS-232C or RS-422 standards. A serial port is a physical interface for communicating digital data between a DTE (Data Terminal Equipment) -usually your computer and a DCE (Data Communication Equipment) – your modem or another serial device. A standard RS-232 cable is used to connect a DCE device to a DTC device via their serial ports.