This is a diagnostics tool included in MessagingToolkit to help you verifying the AT command support of the modem or handset.
First, make sure your modem is connected to your computer either through serial cable, bluetooth or infrared.
Select the correct configuration (port, data bits, baud rate). Enter the PIN if it is configured in the SIM card. Click Next once your gateway is connected.
Click Start Diagnosing, you should see output similar to following