VB.NET Send AT commands to Remote Modem via Dial Up

I am writing a VB.NET application that will us a modem attached to a server to dial up a CDMA modem (Metrum) sitting in the field and send it AT commands to switch the modem from Dial Up mode to IP mode. I was able to telnet into the modem passing it AT commands to switch it from IP to Dial Up but I need to be able to switch it back. Suggestions? I have a internal modem in my laptop I can test with, but the modem we will be using to dial out will be different, we have not purchased on yet.

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I figured it out. I mapped a modem to a com port 5. Then execute the code below. Not to complicated and worked like a charm.

    Public Function ComSwitch(ByVal PhoneNumber As String, ByVal ComPort As String) As Boolean
        Dim ConnectionTime As Integer = 0
        Dim Command As String = "AT*LISTENMODE=1" 'Tells modem to listen switch to IP mode.
        Try
            ' set buffer size
            modemPort.WriteBufferSize = 8000
 
            'Open Port
            modemPort.Open()
 
            ' initialize modem
            modemPort.Write("ATZ" & vbCrLf)
 
            ' txtPhone.text has the phone number to call
            modemPort.Write("ATDT" & PhoneNumber & vbCrLf)
 
            'Takes 10 to 30 seconds for the modem to pick up so wait for 
            '10 seconds then start waiting for response.
            Thread.Sleep(10000)
            ConnectionTime = 10
 
            'This will wait for 50 seconds for a connection
            'if no connection is established in 50 seconds 
            'close port and return false.
            While Connected = False
                Thread.Sleep(2)
                ConnectionTime += 2
 
                If ConnectionTime >= 60 Then
                    modemPort.Close()
                    Return False
                End If
            End While
 
            'writes the command to the modem to switch to IP mode
            modemPort.Write(Command & vbCrLf)
 
            'Make sure the command was sent before disconnecting
            Thread.Sleep(3000)
 
            'Disconnect from modem
            modemPort.Close()
        Catch ex As Exception
 
        End Try
 
    End Function
 
 
    Private Sub modemPort_DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles modemPort.DataReceived
        'This procedure will wait for the response from the modem
        'it will parse it out and make sure it connected.
        'Still need to finish this code but you get the idea.
        e.ToString()
        Connected = True
    End Sub

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VB.NET Send AT commands to Remote Modem via Dial Up

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General Packet Radio Service (GPRS)

Global System for Mobile Communications (GSM)

Microsoft Visual Basic.Net

.NET

Microsoft Programming

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