Option Strict On : Option Explicit On
Imports System.IO.Ports
Imports System.Threading
 
Public Class Class_COM
    Private WithEvents _serialPort As SerialPort
 
    Public Event ComStateChanged(ByVal sender As Object, e As EventArgs)
    Public Event Datareceived(ByVal sender As Object, data As String)
 
    Public Function OpenCom(ByVal Comport As String) As Boolean
 
        _serialPort = New SerialPort
        _serialPort.PortName = "COM2"
        _serialPort.BaudRate = 115200
        _serialPort.Parity = 0
        _serialPort.DataBits = 8
        _serialPort.StopBits = StopBits.One
        _serialPort.RtsEnable = True
        _serialPort.DtrEnable = True
        _serialPort.Handshake = 0
        _serialPort.ReadTimeout = 500
        _serialPort.WriteTimeout = 500
 
 
        Try
            _serialPort.Open()
            If _serialPort.IsOpen Then
                RaiseEvent ComStateChanged(Me, EventArgs.Empty)
            End If
            Return _serialPort.IsOpen
        Catch ex As Exception
            Return False
        End Try
 
    End Function
 
    Public Function WriteCom(ByVal message As String) As Boolean
        Try
            _serialPort.WriteLine(message)
            Return True
        Catch
            Return False
        End Try
    End Function
 
    Public Function CloseCom() As Boolean
        Try
            _serialPort.Close()
            RaiseEvent ComStateChanged(Me, EventArgs.Empty)
            Return True
        Catch
            Return False
        End Try
    End Function
 
    Public Function comstatus() As Boolean
        Return _serialPort.IsOpen
    End Function
 
    Private Sub DataReceivedHandler(sender As Object, e As  _
      SerialDataReceivedEventArgs) Handles _serialPort.DataReceived
 
        Dim sp As SerialPort = CType(sender, SerialPort)
        Dim indata As String = sp.ReadExisting()
 
        RaiseEvent Datareceived(Me, indata)
    End Sub
 
End Class

Public Class frmCom
 
    Dim WithEvents myCom As New Class_COM
 
    Dim WithEvents btnSenden As New Button _
        With {.Parent = Me, .Text = "Senden"}
 
    Dim txtState As New TextBox _
        With {.Parent = Me, .Top = 50}
    Dim txtData As New TextBox _
        With {.Parent = Me, .Top = 100}
 
    Private Sub frmCom_Load(sender As System.Object, _
        e As System.EventArgs) Handles MyBase.Load
 
        If Not myCom.OpenCom("xxxx") Then
            MsgBox("Port kann nicht geöffnet werden")
        End If
 
    End Sub
 
    Private Sub mycom_ComStateChanged(sender As Object, _
        e As System.EventArgs) Handles myCom.ComStateChanged
 
        txtState.Text = If(myCom.comstatus, "Open", "Close")
    End Sub
 
    Private Sub mycom_Datareceived(sender As Object, _
        data As String) Handles myCom.Datareceived
 
        txtData.Text = data
    End Sub
 
    Private Sub btnSenden_Click(sender As Object, _
        e As System.EventArgs) Handles btnSenden.Click
 
        myCom.WriteCom("XXX")
    End Sub
End Class