How to Know Active COM port Dynamically

[sudheer168]

Hi,
I am using QT4.4 on windows to develop a GUI application which will communicate with a Electronic Unit (named data processing system) using MOXA USB which I have bought in market, they provide the drivers to make work.If I insert the USb cable and install the drivers of it ,it will be installed to that COM port (either it is COM1/COM2/COM3).Now I am using QExtSerialport library to make communicate through the USB. In this QExtSerialport library they provided member functions to set the COM and to open it .Now ,what I am doing is ,I am manually looking the system device drivers to make confirm in which COM the USB is installed and knowing this I am writing code as QExtserial port port->setCom (COM NAME).But I want to kknow Dynamically through Program ,that which Comport is active with MOXA USB .How can I know the COM number Dynamically to make that port open using QT.
So please help me to solve this problem .

With Regards
Sudheer