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Imports System.Management

Public Class Form1
    Public Function ModemConnected() As String
        Dim modems As String = ""

        Try
            Dim Searcher As New ManagementObjectSearcher("root\CIMV2", "SELECT * FROM Win32_POTSModem")
            For Each queryObj As ManagementObject In Searcher.Get()
                If queryObj("Status") = "OK" Then
                    modems = modems & (queryObj("AttachedTo") & " - " & queryObj("Description") & "***")

                End If
            Next
        Catch ex As Exception
            MsgBox(ex.Message)
            Return ""

        End Try
        Return modems

    End Function
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim ports() As String
        ports = Split(ModemConnected(), "***")
        For i As Integer = 0 To ports.Length - 2
            ComboBox1.Items.Add(ports(i))

        Next
        Try
            ComboBox1.SelectedIndex = 0
        Catch ex As Exception

        End Try
    End Sub

    Private Sub btnConnect_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnConnect.Click
        If btnConnect.Text = "Connect" Then
            Try
                Dim df() As String = ComboBox1.Text.Split(" - ")
                With SerialPort1
                    .PortName = df(0).ToString
                    .BaudRate = 9600
                    .Parity = IO.Ports.Parity.None
                    .DataBits = 8
                    .StopBits = IO.Ports.StopBits.One
                    .Handshake = IO.Ports.Handshake.None
                    .RtsEnable = True
                    .ReceivedBytesThreshold = 1
                    .NewLine = vbCr
                    .ReadTimeout = 1000
                    .Open()

                End With
            Catch ex As Exception
                MsgBox(ex.Message)
                Exit Sub

            End Try
            If SerialPort1.IsOpen = True Then
                With Label3
                    .Text = "Connected"
                    .ForeColor = Color.Green

                End With
                btnConnect.Text = "Diconnect"
            End If
        Else
            Try
                SerialPort1.Close()
            Catch ex As Exception
                MsgBox(ex.Message)
                Exit Sub
            End Try
            With Label3
                .Text = "Not Connected"
                .ForeColor = Color.Red

            End With
            btnConnect.Text = "Connect"
        End If
    End Sub

    Private Sub Output_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Output.TextChanged
        Output.SelectionStart = Output.Text.Length - 1
        Output.ScrollToCaret()

    End Sub

    Private Sub btnSend_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSend.Click
        Try
            SerialPort1.WriteLine(Input.Text & vbCr)

        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
        For Each d As String In input.Items
            If input.Text = d Then Exit Sub
        Next
        input.Items.Add(input.Text)
        input.SelectAll()

    End Sub

    Private Sub SerialPort1_DataReceived(ByVal sender As System.Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
        Invoke(Sub() Output.Text &= vbCr & vbCr & SerialPort1.ReadExisting())
    End Sub

    Private Sub input_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles input.SelectedIndexChanged

    End Sub

    Private Sub input_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles input.KeyPress
        If e.KeyChar = vbCr Then
            btnSend.PerformClick()

        End If
    End Sub
End Class