'Einrichten der Com
Private Sub verbinden_Click(ByVal sender As System.Object, ByVal e As _
  System.EventArgs) Handles verbinden.Click
        With SerialPort1
            If Not .IsOpen Then
                Try
                    .PortName = ComboBox1.Text
                    .BaudRate = 38400
                    .DataBits = 8
                    .Parity = Parity.None
                    .StopBits = StopBits.One
                    .WriteTimeout = 100                ' 1000 ms = 1 Sek.
                    .ReadTimeout = 100                 ' 1000 ms = 1 Sek.
                    .Open()
                    verbinden.BackColor = Color.Green
                    verbinden.Text = "Verbunden"
                Catch ex As Exception
                    MessageBox.Show(ex.Message, "Fehler beim Open", _
                      MessageBoxButtons.OK, MessageBoxIcon.Error)
                    Exit Sub
                End Try
            End If
        End With
    End Sub
 
...
Me.SerialPort1.ReceivedBytesThreshold = 1  'nach 1 Bytes DataReceived Event 
' auslösen
...
   Sub SerialPort1_DataReceived(ByVal sender As Object, ByVal e As _
     System.IO.Ports.SerialDataReceivedEventArgs) Handles _
     SerialPort1.DataReceived
        With SerialPort1
            Try
                Bufferbyte = .ReadByte
                Select bytezähler
                    Case 0
                        If Bufferbyte = &HFF Then  'Start
                            bytezähler = 1
                        End If
                    Case 1
                        If Bufferbyte = &H30 Then   'Version
                            bytezähler = 2
                        Else
                            bytezähler = 0
                        End If
                    Case 2
                        If Bufferbyte = &H1 Then    'Ziel
                            bytezähler = 3
                        Else
                            bytezähler = 0
                        End If
                    Case 3
                        quelle = Bufferbyte         'Quelle
                        bytezähler = 4
                    Case 4
                        anzahlpara = Bufferbyte * 255
                        bytezähler = 5
                    Case 5
                        anzahlpara = anzahlpara + Bufferbyte
                        bytezähler = 6
                        zahler = 0
                    Case 6
                        ByteArray(zähler) = Bufferbyte
                        zähler += 1
                        Debug.Print(zähler)
                        If zähler = anzahlpara - 1 Then
                            MsgBox("hallo")
                        End If
                End Select
 
            Catch ex As Exception
                MessageBox.Show(ex.Message, "Fehler beim Empfangen ComPort...")
                If SerialPort1.IsOpen Then .DiscardInBuffer()
            End Try
        End With
    End Sub