The com0com Distributive
The MasterOPC Universal Modbus Server delivery kit includes a distributive of a null-modem emulator com0com (32-bit version 2.2.2.0; see also Main Characteristics and License Policy ).
The official site of the utility is
https://sourceforge.net/projects/com0com/
This utility is destined to create a virtual pair of COM ports. The utility can be used together with ModRSSim to simulate a Modbus RTU device. If you do not need simulation of Modbus devices. or if you need only simulation of a Modbus TCP device, do not install the utility.
That distributive consists of the following two files:
setup.exe – the com0com setup wizard, an executive file. Note that the version delivered is for 32-bit OS. If your OS is 64-bit, download the respective version of com0com from the utility site.
Readme.txt – emulator description in English
When installing MasterOPC Universal Modbus Server, those files are unpacked into the folder <MasterOPC Universal Modbus Server installation folder>\com0com.