AT Command Tester is an online tool to test GSM modem features. It uses serial port of the device for communication.
In order to check if you can successfuly communicate with the device over a serial connection, you can use a free tool call Putty.
Download the Putty tool from here
Configure the Putty tool as shown below. Choose “Serial” for “Connection type”. Then choose your port and the modem speed.
After you open with above setup, you should see a console window as shown below. Type ‘AT’ in the console window and press enter. If your modem connection is sucessful, you should see ‘OK’ response in teh console window.
If you are not sure what serial speed your modem is set to, try different speeds (19200, 38400, 57600, 115200) on the Putty conenction.