Dim WithEvents Port As New SerialPort("COM1")
    Dim WithEvents BackgroundWorker1 As System.ComponentModel.BackgroundWorker
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        Me.BackgroundWorker1.RunWorkerAsync()
    End Sub
 
    Private Sub BackgroundWorker1_DoWork(ByVal sender As Object, ByVal e As _
      System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
 
        Dim SendString, ReceiveString As String
 
        SendString = "Test"
 
        'Port öffnen und senden
        Me.Port.Open()
        Me.Port.WriteLine(SendString)
 
        'Antwort abwarten
        While Me.Port.BytesToRead = 0
            Threading.Thread.Sleep(50)
        End While
 
        ReceiveString = Me.Port.ReadLine()
 
        e.Result = ReceiveString
 
    End Sub
 
    Private Sub BackgroundWorker1_RunWorkerCompleted(ByVal sender As Object, _
      ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles _
      BackgroundWorker1.RunWorkerCompleted
        MsgBox("Habe folgende Antwort erhalten:" + vbCrLf + CStr(e.Result))
    End Sub