PRB: Winsock Control does not Fire Error Event in all Cases

ID: Q244751

The information in this article applies to:

Microsoft Visual Basic Learning, Professional, and Enterprise Editions for Windows, versions 5.0, 6.0

SYMPTOMS

When using the Winsock Control in Visual Basic, setting the LocalPort property to a port value that is already in use on the local computer raises a Visual Basic Run-time error when the Connect or Bind method is called. The Run-time error is as follows:

'10048' - "Address in use".

Normally this could be captured using the Error Event of the Winsock Control, but even when the Error event is present for the control, the Error event is never fired and the Run-time error message box is displayed.

RESOLUTION

A valid workaround is to use Visual Basic's standard Error Handling mechanism to catch the error as illustrated in the following code snippet:


On Error Resume Next
Winsock1.Connect
If Err then 
   ' handle the error here
End if

Simply use the On Error method around the Connect or Bind method of the Winsock Control to capture this error.

MORE INFORMATION

Steps to Reproduce Behavior

Create a New Project.

Add the Winsock Control to the Project.

Place the Winsock Control on the Form.

Add the following code:


Private Sub Form_Load()
  Winsock1.RemoteHost = "localhost"
  Winsock1.RemotePort = 7	' connect to echo server from Simple TCP/IP Services available on NT
  Winsock1.LocalPort = 80	' pick a port that is in use... 80 is IIS (http)  
  Winsock1.Connect  ' this line of code will force the run-time error even the error event is included below
End Sub

Private Sub Winsock1_Error(ByVal Number As Integer, Description As String, ByVal Scode As Long, ByVal Source As String, ByVal HelpFile As String, ByVal HelpContext As Long, CancelDisplay As Boolean)
  CancelDisplay = True
  MsgBox "Error"
End Sub

When this code is run the Winsock1_Error handler is never called even though a Winsock Control error has occurred. Using the work-around mentioned earlier causes Visual Basic's normal error handling to handle the error.

Additional query words:

Keywords : kbnetwork kbAPI kbCtrl kbSDKPlatform kbSDKWin32 kbVBp600 kbDSupport kbGrpNet
Version : WINDOWS:5.0,6.0
Platform : WINDOWS
Issue type : kbprb