Null-modem cable is basically used for communication of two RS-232 "DTE" devices with each other. To create null-modem connection between the devices you need to use two computers or two serial ports of a single computer connected with null-modem cable. The both methods described above are expensive and difficult because of many reasons. The most reliable way to create null-modem connection is using of virtual serial ports emulated by virtual serial port driver and null-modem cable.
Why do you need to emulate serial ports and null-modem connection? There are few main reasons to do it. Firstly, you don’t need to have two computers connected with real null-modem cable. Secondly, there’s no need in a single PC with several free serial ports and additional multi serial port devices which are expensive and bulky. To emulate null-modem connection Virtual Null Modem can be effectively used. The program emulates one or more couples of RS-232 serial ports connected via...