Public Class Form1
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
        SerialPort1.Open()
    End Sub
    Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
        SerialPort1.Close()
    End Sub
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        ' SerialPort1.RtsEnable = Not SerialPort1.RtsEnable
        SerialPort1.DtrEnable = Not SerialPort1.DtrEnable
    End Sub
End Class