Q199856: FIX: SIZE Command Does Not Work in Internet Transfer Control

Article: Q199856
Product(s): Microsoft Visual Basic for Windows
Version(s): 4.0
Operating System(s): 
Keyword(s): kbnokeyword kbDSupport
Last Modified: 15-SEP-2001

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The information in this article applies to:

- Microsoft Visual Basic Professional Edition, 32-bit, for Windows, version 4.0 
- Microsoft Visual Basic Enterprise Edition, 32-bit, for Windows, version 4.0 
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SYMPTOMS
========

When you use the Internet Transfer Control to run the SIZE command,
icResponseCompleted is not returned to the StateChanged event, and you cannot
obtain a size.

CAUSE
=====

This problem occurs because the Internet Transfer Control is not properly
handling the WM_INET_FTPSIZE message.

RESOLUTION
==========

To obtain a file size through a Visual Basic application, you can use the
FtpFindFirstFile and InternetFindNextFile WinInet functions directly.

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 Internet Transfer Control that shipped with Microsoft
Visual Basic 6.0.

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

The following code illustrates the problem:

  Private Sub Command1_Click()
      Inet1.Execute "ftp://server", "size /"
  End Sub

  Private Sub Inet1_StateChanged(ByVal State As Integer)
      Dim vtData As Variant ' Data variable.
      Select Case State
      ' ... Other cases are not shown.

      Case icResponseCompleted ' 12
          vtData = Inet1.GetChunk(1024)
      End Select

      Text1.Text = vtData
  End Sub

An example of the code that is necessary to implement the workaround is available
in the VBFTP.exe sample, which is available from the following Microsoft
Knowledge Base article:

  Q175179 SAMPLE: VBFTP.EXE: Implementing FTP Using WinInet API from VB

This sample uses the FtpFindFirstFile and InternetFindNextFile functions to
populate a tree view of the files that are available on the FTP server. A
WIN32_FIND_DATA structure is passed to these functions that, after the function
is run, will contain the size of the found file. The WIN32_FIND_DATA structure
contains the nFileSizeHigh and nFileSizeLow members, which represent the size of
the file. The Win32 Software Development Kit (SDK) describes these members as
follows:

  nFileSizeHigh
  Specifies the high-order DWORD value of the file size, in bytes. This value is
  zero unless the file size is greater than MAXDWORD. The size of the file is
  equal to (nFileSizeHigh * MAXDWORD) + nFileSizeLow.

  nFileSizeLow
  Specifies the low-order DWORD value of the file size, in bytes.

MAXDWORD is defined in WinNT.h as follows:

  #define MAXDWORD    0xffffffff

This can be defined in Visual Basic as follows:

  Public Const MAXDWORD = &Hffffffff

IMPORTANT: WinInet uses a LIST command to gather information about the files on
an FTP server. Some FTP servers do not return data in a format that WinInet can
parse. In this case, the above work around will not work.

Additional query words: broken

======================================================================
Keywords          : kbnokeyword kbDSupport 
Technology        : kbVBSearch kbAudDeveloper kbVB400Search kbVB400
Version           : :4.0
Issue type        : kbbug
Solution Type     : kbfix

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