Hi Ravi,
I am not sure that I got what do you need to do.
Do you need to test the terminal itself or the end-user software that is designed to use it?
In the latter case your tests will communicate with the tested software and it is not the problem of your tests how the software communicates with the terminal.
In the former case it is good to know how it is possible to communicate with the terminal. I remember that I saw a code samples for TC on how to communicate with the device through COM and LPT ports. Not sure if I saw the samples for, say, WiFi communication but I think that we should start from understanding your exact actual needs.