Public Class Form1
 
    Dim WithEvents SerialPort1 As New System.IO.Ports.SerialPort()
    Dim Wert As String
    Private Delegate Sub DelegateSub()
    Private TextboxAktualisieren As New DelegateSub(AddressOf Wertübergabe)
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
 
        With SerialPort1
            If .IsOpen Then
                .Close()
            End If
            .PortName = "COM1"
            .BaudRate = 9600
            .Parity = IO.Ports.Parity.None
            .DataBits = 8
            .StopBits = IO.Ports.StopBits.One
            .Open()
            Return
        End With
 
    End Sub
 
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button2.Click
 
        End
 
    End Sub
 
    Private Sub SerialPort1_DataReceived(ByVal sender As Object, ByVal e As _
      System.IO.Ports.SerialDataReceivedEventArgs) Handles _
      SerialPort1.DataReceived
 
        Me.Invoke(TextboxAktualisieren)
        Threading.Thread.Sleep(5000)
 
    End Sub
 
    Private Sub Wertübergabe()
 
        TextBox1.Text = SerialPort1.ReadExisting()
        MsgBox("Wert wird übergeben!")
 
    End Sub
 
End Class