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Q245159: FIX: SendData Only Works Over the Latest Connection

Article: Q245159
Product(s): Microsoft Visual Basic for Windows
Version(s): 5.0,6.0
Operating System(s): 
Keyword(s): kbnetwork kbCtrl kbSDKPlatform kbSDKWin32 kbVBp500 kbVBp600 kbWinsock kbDSupport kbGrpD
Last Modified: 13-MAR-2002

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The information in this article applies to:

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

For a 32-bit Visual Basic application with multiple Winsock Control objects that
maintain TCP connections to other socket applications, SendData() only works
over the most recently established connection. This behavior is reproducible on
versions prior to and include Microsoft Visual Studio SP3.

CAUSE
=====

The event messages associated with each SendData() are flushed from the message
queue by the latest socket connection. This causes data to queue up and with no
event messages available to start the data send process for previous
connections.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This bug was corrected in the latest service pack for
Visual Studio 6.0.

For additional information about Visual Studio service packs, click the article
numbers below to view the articles in the Microsoft Knowledge Base:

  Q194022 INFO: Visual Studio 6.0 Service Packs, What, Where, Why

  Q194295 HOWTO: Tell That a Visual Studio Service Pack Is Installed

You can download the latest Visual Studio service pack from the following
Microsoft Web site:

  Visual Studio Product Updates
  (http://msdn.microsoft.com/vstudio/downloads/updates.asp)

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

To reproduce the problem assuming an application maintains an array of three
Winsock Control objects, each of controls has established a connection with its
peer side over TCP. Label the connections as C1, C2, and C3 based on the order
the connections are established, with C3 as the most recently established
connection. If you attempt to do the following:

     Private Sub cmdSendData_Click()
         Dim i As Long
         For i = 1 To iIndex
             If (socks(i).State = sckConnected) Then
                 socks(i).SendData txtSendData.Text
             End If
         Next i
     End Sub

Only the peer side of C3 connection get the messages. If you disconnect C3, the
peer side of C2, which becomes the most recent connection at the time, will
start to receive messages intended for it.

REFERENCES
==========

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

  Q183987 PRB: SendData Method Generates Error 40006

Additional query words: mswinsck.ocx sp4

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Keywords          : kbnetwork kbCtrl kbSDKPlatform kbSDKWin32 kbVBp500 kbVBp600 kbWinsock kbDSupport kbGrpDSNet kbVS600sp4fix kbVS600sp5fix 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVB500 kbVB600
Version           : :5.0,6.0
Issue type        : kbbug
Solution Type     : kbfix

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