Public Class Form1
    Dim WithEvents SerialPort As New IO.Ports.SerialPort
 
    Private Sub MenuItem2_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MenuItem2.Click
        With SerialPort
            .PortName = "COM7" 'oder "COM7" , geht auch nicht
            .BaudRate = 9600
            .Parity = IO.Ports.Parity.None
            .DataBits = 8
            .StopBits = IO.Ports.StopBits.One
        End With
        SerialPort.Open()
        MenuItem2.Enabled = False
        MenuItem3.Enabled = True
    End Sub
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
        'Hier soll er nach allen verfügbaren Com Ports suchen:
        For i As Integer = 0 To _
            cbxcomports.Items.Add(IO.Ports.SerialPort.GetPortNames(i))
            MenuItem3.Enabled = False
        Next
 
    End Sub
 
    Private Sub MenuItem3_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MenuItem3.Click
        SerialPort.Close()
        MenuItem3.Enabled = False
        MenuItem2.Enabled = True
    End Sub
 
 
    Private Sub btnSenden_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles btnSenden.Click
        SerialPort.Write(tbxeingabe.Text & vbCrLf)
        With tbxmessaging
            .Text = "Gesendet: " & tbxeingabe.Text
            .ScrollToCaret()
        End With
        tbxeingabe.Text = String.Empty
    End Sub
End Class