FIX: Internet Transfer Control 5.0 "POST" Request Doesn't Work

• Microsoft Visual Basic Control Creation, Learning, Professional, and Enterprise Editions for Windows, version 5.0

SYMPTOMS

The Internet Transfer Control 5.0 "POST" request does not work as described in the documentation provided by Microsoft. The input data parameter of the Execute method is not being sent correctly to the web server when "POST" is specified.

RESOLUTION

The Internet Transfer Control 5.0 "POST" request does not work from Visual Basic 5.0. You need to use the WinInet APIs that are included with the ActiveX SDK to PostData to your server. Specifically, the InternetOpen, InternetConnect, HttpOpenRequest, and HttpSendRequest are the WinInet APIs you need to use. In the sample code below, you will connect to //webserver then post to page /generic.asp.

1. Start a new Standard EXE project. Form1 is added 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 InternetCloseHandle Lib "wininet.dll" _
            (ByVal hInternetHandle As Long) As Boolean
    




3. From the Project menu, choose Components, and then select the Internet Transfer Control 5.0 into the project if it is not already loaded.



4. Place an Internet Transfer Control 5.0 (Inet1) on Form1.



5. 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, _
                                  "webserver", _
                                  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, _
                                     "POST", _
                                     "/generic.asp", _
                                     "HTTP/1.0", _
                                     vbNullString, _
                                     0, _
                                     INTERNET_FLAG_RELOAD, _
                                     0)
   
                  If hHttpOpenRequest <> 0 Then
                     Dim lpszPostData As String
                     Dim lPostDataLen As Long
   
                     lpszPostData = "lname=Doe&fname=John"
                     lPostDataLen = Len(lpszPostData)
                     bRet = HttpSendRequest(hHttpOpenRequest, _
                            vbNullString, _
                            0, _
                            lpszPostData, _
                            lPostDataLen)
                     'Close all handles
                     bRet = InternetCloseHandle(hHttpOpenRequest)
                  End If
                  bRet = InternetCloseHandle(hInternetConnect)
               End If
               bRet = InternetCloseHandle(hInternetOpen)
            End If
   
         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 "lname=Doe&fname=John" will be posted to your server.
   
   NOTE: You will have to replace //webserver/generic.asp with your server page that is expecting the posted information. You will also need to replace "lname=Doe&fname=John" with the information you want posted.

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

Q171554 : INFO: Visual Basic 5.0 Fixes in Visual Studio 97 Service Pack 2

MORE INFORMATION

Steps to Reproduce Behavior

1. Start a new Standard EXE project. Form1 is added 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 an Internet Transfer Control 5.0 (Inet1) on Form1.



4. Place a CommandButton (Command1) on Form1 and add the following code:
   

   
         Private Sub Command1_Click()
            Dim strURL As String, strFormData As String
            strURL = "http://webserver/generic.htm"
            strFormData = "fname=randy&lname=morgan"
            Inet1.Execute strURL, "Post", strFormData, _
               "Content-Type: application/x-www-form-urlencoded"
         End Sub
    




5. 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 http://webserver/generic.htm.

REFERENCES

ActiveX SDK

Keywords : kbVBp500 kbVS97sp2fix VBKBAX VBKBComp VBKBCtrl VBKBInt kbvbp500sp2fix
Version : 5.0
Platform : WINDOWS
Issue type : kbbug