Com Ports and the MSComm Control

For this example to work, ensure that the following properties are set.

After this, firstly, we need to open the COM port. To do this, simply set the PortOpen property to true:

MSComm1.PortOpen = True

Then, we need to send the command. For this example, we will ask your modem to dial your own number. So, the command will be

ATDT01992245365

AT tells the modem that a command is coming up. DT tells it to dial the upcoming number using Tone dial. Then the text in red is the number to dial. Change the number in red to your own number. We also need to add a Chr$(13) after the command. You nearly always need to do this. So, to send this command, we enter

MSComm1.Output = "ATDT01992245365" & Chr$(13)

You could of course, substitute the telephone number with a Text box, so that the user could enter the number:

MSComm1.Output = "ATDT" & txtNumber.Text & Chr$(13)

Then, the modem will attempt to dial the number. If you want a list of the main commands to control a modem, click here. Of course, if the device connected to the COM port is not a modem, you will need to know what commands to send it.

At the moment, we have no way of knowing if the dialing was successful. This is where the OnComm event is useful. This is discussed in the next section.