Private Sub SerialPort1_DataReceived(ByVal sender As Object, ByVal e As _
  System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
        Dim enc As System.Text.Encoding = New System.Text.ASCIIEncoding()
        With SerialPort1
            For I As Integer = 1 To .BytesToRead
                    Dim ByteArray() As Byte = {.BaseStream.ReadByte}
                    PufferString = enc.GetString(ByteArray)
                    Me.Invoke(Datenanzeigen)
             Next
         End With
End Sub
 
Private Delegate Sub DelegateSub()
Private Datenanzeigen As New DelegateSub(AddressOf Anzeigen)
 
Private Sub Anzeigen()
        TextBox1.AppendText(PufferString)
        TextBox1.ScrollToCaret()
End Sub
 
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
  System.EventArgs) Handles Button1.Click
        If SerialPort1.IsOpen Then
                SerialPort1.Close() ' Port wieder Schließen
         End If
End Sub