Option Explicit

Dim MySock As Object
Const PortsChecked = 200

Private Sub Command1_Click()
Timer1.Enabled = True
Timer1.Interval = 1000
End Sub

Private Sub Command2_Click()
Timer1.Interval = 0
Timer1.Enabled = False
End Sub

Private Sub Timer1_Timer()

Dim X As Integer
List1.Clear
For X = 1 To PortsChecked
DoEvents
Text1.Text = X
Set MySock = CreateObject("MSWinsock.Winsock.1")
MySock.LocalPort = X

On Error Resume Next

MySock.Listen
' If we get an error, the port is busy.

If Err.Number = 10048 Then List1.AddItem X
' Log Active port # to list box.
Err.Number = 0
End If

MySock.Close
Set MySock = Nothing
Next X

End Sub

Private Sub Form_Load()
Label1.Caption = "Checking Port #"
Label2.Caption = "Ports In Use"
Command1.Caption = "Start"
Command2.Caption = "End"
Text1.Locked = True
End Sub