Public Class Hauptfenster
    Inherits System.Windows.Forms.Form
 
    Dim InfoPortOpen As String = "Schnittstelle wird von einem anderen Programm" & _
      "verwendet"
    Dim InfoPortClosed As String = "Datenkommunikation erfolglos, da" & _
    "Schnittstelle geschlossen: "
    Dim WithEvents SerialPort As New System.IO.Ports.SerialPort("COM3", 115200, _
    Parity.None, 8, StopBits.One)
    Private Delegate Sub DelegateSub()
 
    Public Sub Me_Load(ByVal sender As Object, ByVal e As System.EventArgs) _
      Handles MyBase.Load
 
    End Sub
 
    Public Sub CommStart()
        With SerialPort
            If .IsOpen Then
                MsgBox(InfoPortOpen, MsgBoxStyle.Critical)
            Else
                .Open()
            End If
            Return
        End With
    End Sub
 
    Public Sub CommStop()
        With SerialPort
            .Close()
            Return
        End With
    End Sub
 
    Public Sub DataStart()
        Dim FomStart As Byte = 85
        Dim FomDeviceID As Byte = 255
        Dim FomSize As Byte = 4
        Dim FomFunction As Byte = 1
        Dim FomData As Byte = 0
 
        If SerialPort.IsOpen Then
            SerialPort.Write(Hex(FomStart))
            SerialPort.Write(Hex(FomDeviceID))
            SerialPort.Write(Hex(FomSize))
            SerialPort.Write(Hex(FomFunction))
            SerialPort.Write(Hex(FomData))
        Else
            MsgBox(InfoPortClosed + SerialPort.PortName, MsgBoxStyle.Critical)
        End If
    End Sub