Q171271: FIX: Internet Transfer Control 5.0 Has Bug with "HEAD" Request
Article: Q171271
Product(s): Microsoft Visual Basic for Windows
Version(s): 5.0
Operating System(s):
Keyword(s): kbVBp500 kbVS97sp2fix kbvbp500sp2fix
Last Modified: 14-JAN-2001
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The information in this article applies to:
- Microsoft Visual Basic Control Creation Edition for Windows, version 5.0
- Microsoft Visual Basic Professional Edition for Windows, version 5.0
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SYMPTOMS
========
The Internet Transfer Control 5.0 "HEAD" request does not work based on the
documentation provided by Microsoft. There is no header information being
returned when the Execute method and "HEAD" request are sent to the web server.
RESOLUTION
==========
The Internet Transfer Control 5.0 "HEAD" request does not work from Visual Basic
5.0. You need to use the WinInet APIs that are included with the ActiveX SDK to
get header information from your server. Specifically the InternetOpen,
InternetConnect, HttpOpenRequest, HttpSendRequest, and HttpQueryInfo are the
WinInet APIs you need to use. In the sample code below, get the header
information from:
http://www.microsoft.com/default.htm
The following code can be used to work around this problem:
1. Run Visual Basic or, if Visual Basic is already running, choose New Project
from the File menu (ALT, F, N). Form1 is created by default.
2. Add the following code to the general declarations section of Form1:
Private Declare Function InternetOpen Lib "wininet.dll" _
Alias "InternetOpenA" _
(ByVal lpszCallerName As String, _
ByVal dwAccessType As Long, _
ByVal lpszProxyName As String, _
ByVal lpszProxyBypass As String, _
ByVal dwFlags As Long) As Long
Private Declare Function InternetConnect Lib "wininet.dll" _
Alias "InternetConnectA" _
(ByVal hInternetSession As Long, _
ByVal lpszServerName As String, _
ByVal nProxyPort As Integer, _
ByVal lpszUsername As String, _
ByVal lpszPassword As String, _
ByVal dwService As Long, _
ByVal dwFlags As Long, _
ByVal dwContext As Long) As Long
Private Declare Function HttpOpenRequest Lib "wininet.dll" _
Alias "HttpOpenRequestA" _
(ByVal hInternetSession As Long, _
ByVal lpszVerb As String, _
ByVal lpszObjectName As String, _
ByVal lpszVersion As String, _
ByVal lpszReferer As String, _
ByVal lpszAcceptTypes As Long, _
ByVal dwFlags As Long, _
ByVal dwContext As Long) As Long
Private Declare Function HttpSendRequest Lib "wininet.dll" _
Alias "HttpSendRequestA" _
(ByVal hHttpRequest As Long, _
ByVal sHeaders As String, _
ByVal lHeadersLength As Long, _
ByVal sOptional As String, _
ByVal lOptionalLength As Long) As Boolean
Private Declare Function HttpQueryInfo Lib "wininet.dll" _
Alias "HttpQueryInfoA" _
(ByVal hHttpRequest As Long, _
ByVal lInfoLevel As Long, _
ByVal sBuffer As Any, _
ByRef lBufferLength As Long, _
ByRef lIndex As Long) As Boolean
Private Declare Function InternetCloseHandle Lib "wininet.dll" _
(ByVal hInternetHandle As Long) As Boolean
3. From the Project menu, choose Components, and select the Internet Transfer
Control 5.0 into the project if it is not already loaded.
4. Place a Internet Transfer Control 5.0(Inet1) on Form1.
5. Place a ListBox Control(List1) on Form1.
6. Place a CommandButton (Command1) on Form1 and add the following code.
Private Sub Command1_Click()
Dim hInternetOpen As Long
Dim hInternetConnect As Long
Dim hHttpOpenRequest As Long
Dim bRet As Boolean
hInternetOpen = 0
hInternetConnect = 0
hHttpOpenRequest = 0
' Use registry access settings.
Const INTERNET_OPEN_TYPE_PRECONFIG = 0
hInternetOpen = InternetOpen("http generic", _
INTERNET_OPEN_TYPE_PRECONFIG, _
vbNullString, _
vbNullString, _
0)
If hInternetOpen <> 0 Then
' Type of service to access.
Const INTERNET_SERVICE_HTTP = 3
Const INTERNET_DEFAULT_HTTP_PORT = 80
hInternetConnect = InternetConnect(hInternetOpen, _
"http://www.microsoft.com/default.htm", _
INTERNET_DEFAULT_HTTP_PORT, _
vbNullString, _
"HTTP/1.0", _
INTERNET_SERVICE_HTTP, _
0, _
0)
If hInternetConnect <> 0 Then
' Brings the data across the wire even if it locally cached.
Const INTERNET_FLAG_RELOAD = &H80000000
hHttpOpenRequest = HttpOpenRequest(hInternetConnect, _
"HEAD", _
vbNullString, _
vbNullString, _
vbNullString, _
0, _
INTERNET_FLAG_RELOAD, _
0)
If hHttpOpenRequest <> 0 Then
bRet = HttpSendRequest(hHttpOpenRequest, _
vbNullString, _
0, _
vbNullString, _
0)
' Headers to query
Const HTTP_QUERY_CONTENT_TYPE = 1
Const HTTP_QUERY_VERSION = 18
Const HTTP_QUERY_SERVER = 37
Const HTTP_QUERY_REQUEST_METHOD = 45
If bRet Then
Dim sBuff As String * 1024
Dim lBuffLen As Long
lBuffLen = Len(sBuff)
'response headers
If (HttpQueryInfo(hHttpOpenRequest, _
HTTP_QUERY_CONTENT_TYPE, sBuff, lBuffLen, 0) _
= 1) Then
List1.AddItem sBuff
End If
If (HttpQueryInfo(hHttpOpenRequest, _
HTTP_QUERY_VERSION, sBuff, lBuffLen, 0) _
= 1) Then
List1.AddItem sBuff
End If
If (HttpQueryInfo(hHttpOpenRequest, _
HTTP_QUERY_SERVER, sBuff, lBuffLen, 0) _
= 1) Then
List1.AddItem sBuff
End If
If (HttpQueryInfo(hHttpOpenRequest, _
HTTP_QUERY_REQUEST_METHOD, sBuff, lBuffLen, 0) _
= 1) Then
List1.AddItem sBuff
End If
End If
End If
End If
End If
' Close all handles
If hInternetOpen <> 0 Then
bRet = InternetCloseHandle(hInternetOpen)
End If
If hInternetConnect <> 0 Then
bRet = InternetCloseHandle(hInternetConnect)
End If
If hHttpOpenRequest <> 0 Then
bRet = InternetCloseHandle(hHttpOpenRequest)
End If
End Sub
7. From the Run menu, choose Start (ALT, R, S), or press the F5 key to run the
program. Press the Command1 button and garbage will be posted to your server.
STATUS
======
Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This bug has been fixed in Visual Studio 97 Service
Pack 2.
For more information on the Visual Studio 97 Service Pack 2, please see the
following article in the Microsoft Knowledge Base:
Q170365 : INFO: Visual Studio 97 Service Packs - What, Where, and Why
For a list of the Visual Basic 5.0 bugs that were fixed in the Visual Studio 97
Service Pack 2, please see the following article in the Microsoft Knowledge
Base:
Q171554 : INFO: Visual Basic 5.0 Fixes in Visual Studio 97 Service Pack 2
MORE INFORMATION
================
Steps to Reproduce Behavior
---------------------------
1. Run Visual Basic, or if Visual Basic is already running, choose New Project
from the File menu (ALT, F, N). Form1 is created by default.
2. From the Project menu, choose Components, and select the Internet Transfer
Control 5.0 into the project if it is not already loaded.
3. Place a Internet Transfer Control 5.0(Inet1) on Form1.
4. Place a ListBox Control(List1) on Form1.
5. Place a CommandButton (Command1) on Form1 and add the following code.
Private Sub Command1_Click()
Dim strURL As String
strURL = "http://www.microsoft.com/default.htm"
Inet2.Execute URL:=strURL, Operation:="HEAD"
End Sub
6. From the Run menu, choose Start (ALT, R, S) or press the F5 key to run the
program. Press the Command1 button and garbage will be posted to your server.
REFERENCES
==========
ActiveX SDK
======================================================================
Keywords : kbVBp500 kbVS97sp2fix kbvbp500sp2fix
Technology : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVBA500Search kbVB500 kbZNotKeyword3
Version : 5.0
Issue type : kbbug
Solution Type : kbfix
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