DOCUMENT:Q194938  24-JUL-2001  [vbwin]
TITLE   :HOWTO: Monitor TCP/IP Ports in Use
PRODUCT :Microsoft Visual Basic for Windows
PROD/VER::5.0,6.0
OPER/SYS:
KEYWORDS:kbcode kbCtrl kbVBp kbVBp500 kbVBp600 kbGrpDSVB kbDSupport kbCodeSam

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The information in this article applies to:

 - Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0 
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SUMMARY
=======

This article describes how to monitor whether a TCP/IP port is in use.

MORE INFORMATION
================

There are times when it is necessary to know or monitor whether a port is in
use. The following sample demonstrates how this is done.

1. Create a new Standard EXE project. Form1 is created by default.

2. Add 1 Timer, 2 Labels, 1 Listbox, 1 TextBox and 2 CommandButton controls to
   Form1. Position Label1 above Text1 and Label2 above List1.

3. Set the Sorted property of List1 to True.

4. Add the following code to the General Declarations section of Form1:

         Option Explicit

         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
               WinSock1.LocalPort = X
               On Error Resume Next
               WinSock1.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

               WinSock1.Close
            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

5. Run the program. If, for example, you have an active DCOM connection, you
   should see 135 displayed in the ListBox.

   To change the number of ports checked, modify the constant PortsChecked. To
   change the amount of time between samples modify the constant TimerInt.

REFERENCES
==========

For additional information, please see the following article in the Microsoft
Knowledge Base:

   Q173619 PRB: Winsock Control Generates Error 10048 - Address in Use

Also search Visual Basic Help for "Using the Winsock Control."

(c) Microsoft Corporation 1998, All Rights Reserved.
Contributions by Richard T. Edwards, Microsoft Corporation


Additional query words:

======================================================================
Keywords          : kbcode kbCtrl kbVBp kbVBp500 kbVBp600 kbGrpDSVB kbDSupport kbCodeSam 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVB500 kbVB600
Version           : :5.0,6.0
Issue type        : kbhowto

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