A serial port driver to help you with your work. com0com is a hansy, easy to use kernel-mode virtual serial port driver. You can create an unlimited number of virtual COM port pairs and use any pair to connect one COM port based application to another.
The Null-modem emulator is an open source kernel-mode virtual serial port driver for Windows, available freely under GPL license.
The Null-modem emulator allows you to create an unlimited number of virtual COM port pairs and use any pair to connect one COM port based application to another. Each COM port pair provides two COM ports. The output to one port is the input from other port and vice versa.
The Null-modem emulator can be used to provide serial interface for device emulators. In this case the device emulation program uses one port of the pair and the other port can be used by Windows or DOS application that requires a COM port to communicate with the device. For example, to send/receive faxes over IP you can connect Windows Fax application to t38modem ( T38FAX Pseudo Modem , part of the t38modem project ) via virtual COM port pair.
The license of this software is Free, you can free download and free use this protocol analyzer software.