VB.Net อยากทราบการเขียน Code เพื่อเช็คว่า Port อะไรบ้างที่ถูกเปิดอยู่

Private Sub Timer1_Tick(ByVal sender As System.Object, _
            ByVal e As System.EventArgs) Handles Timer1.Tick
    'Set the host and port and counter
    counter = counter + 1 'counter is for the timer
    TextBox2.Text = counter
    host = TextBox1.Text
    port = TextBox2.Text
    ' Next part creates a socket to try and connect 
    ' on with the given user information.
 
    Dim hostadd As System.Net.IPAddress = _
      System.Net.Dns.GetHostEntry(host).AddressList(0)
    Dim EPhost As New System.Net.IPEndPoint(hostadd, port)
    Dim s As New System.Net.Sockets.Socket(_
      System.Net.Sockets.AddressFamily.InterNetwork, _
    System.Net.Sockets.SocketType.Stream, _
      System.Net.Sockets.ProtocolType.Tcp)
    Try
        s.Connect(EPhost)
    Catch
    End Try
    If Not s.Connected Then
        ListBox1.Items.Add("Port " + port.ToString + " is not open")
    Else
        ListBox1.Items.Add("Port " + port.ToString + " is open")
        ListBox2.Items.Add(port.ToString)
    End If
    Label3.Text = "Open Ports: " + ListBox2.Items.Count.ToString
End Sub