Dialer

This example allows you to use the MS Comm control to dial a telephone number.

First, add the MSComm control to your form (you will need to add it to your toolbox by going to Project|Components). Next, add a label called lblMsg, and two command buttons called cmdDial and cmdCancel. Finally, add the code below. Note that you will need to change the Com port property (that is set in the Dial sub) to the COM port your modem uses. This is usually 1-4.

Option Explicit

' This flag is set when the user chooses Cancel.
Dim CancelFlag

Private Sub cmdCancel_Click()
    ' CancelFlag tells the Dial procedure to exit.
    CancelFlag = True
    cmdCancel.Enabled = False
End Sub

Private Sub Dial(Number As String)
    Dim DialString As String, FromModem As String, dummy As String

    ' AT is the Hayes compatible ATTENTION command and is required to send commands to the modem.
    ' DT means "Dial Tone." The Dial command uses touch tones, as opposed to pulse (DP = Dial Pulse).
    ' Numbers is the phone number being dialed.
    ' A semicolon tells the modem to return to command mode after dialing (important).
    ' A carriage return, vbCr, is required when sending commands to the modem.
    DialString = "ATDT" + Number + ";" + vbCr

    ' Communications port settings.
    ' Assuming that a mouse is attached to COM1, CommPort is set to 2
    MSComm1.CommPort = 3
    MSComm1.Settings = "9600,N,8,1"
   
    ' Open the communications port.
    On Error Resume Next
    MSComm1.PortOpen = True
    If Err Then
       MsgBox "COM" & MSComm1.CommPort & ": not available. Change the CommPort property to another port."
       Exit Sub
    End If
   
    ' Flush the input buffer.
    MSComm1.InBufferCount = 0
   
    ' Dial the number.
    MSComm1.Output = DialString
   
    ' Wait for "OK" to come back from the modem.
    Do
       dummy = DoEvents()
       ' If there is data in the buffer, then read it.
       If MSComm1.InBufferCount Then
          FromModem = FromModem + MSComm1.Input
          ' Check for "OK".
          If InStr(FromModem, "OK") Then
             ' Notify the user to pick up the phone.
             Beep
             MsgBox "Please pick up the phone and either press Enter or click OK"
             Exit Do
          End If
       End If
       
       ' Did the user choose Cancel?
       If CancelFlag Then
          CancelFlag = False
          Exit Do
       End If
    Loop
   
    ' Disconnect the modem.
    MSComm1.Output = "ATH" + vbCr
   
    ' Close the port.
    MSComm1.PortOpen = False
End Sub

Private Sub cmdDial_Click()
    Dim Number As String, Temp As String
   
    cmdDial.Enabled = False
    cmdCancel.Enabled = True
   
    ' Get the number to dial.
    Number = InputBox("Enter phone number:", Number)
        If Number = "" Then Exit Sub
    Temp = lblMsg
    lblMsg = "Dialing - " + Number
   
    ' Dial the selected phone number.
    Dial Number

    cmdDial.Enabled = True
    cmdCancel.Enabled = False

    lblMsg = Temp
End Sub

Private Sub Form_Load()
    ' Setting InputLen to 0 tells MSComm to read the entire
    ' contents of the input buffer when the Input property
    ' is used.
    MSComm1.InputLen = 0
   
End Sub