Weird download problem

Hi, I am making a small application to automatically download an image that updates every hour. It works, except the application seems to download duplicates of the same image, even though when I visit the URL myself, it shows the newest image.

I thought something might have been in the cache, and it was just using that instead. I have inserted some cache clearing code, however was just wondering (While I wait for the hour :o ) if anyone had any other idea's as to why it would do this?

My code (without cache clearing stuff)

Code:

---

Dim Hour As Integer

Private Declare Function URLDownloadToFile Lib "urlmon" Alias _
    "URLDownloadToFileA" (ByVal pCaller As Long, ByVal szURL As String, _
    ByVal szFileName As String, ByVal dwReserved As Long, _
    ByVal lpfnCB As Long) As Long
   
Dim errcode As Long
Dim url As String
Dim localFileName As String



Private Sub StartBtn_Click()
Timer1.Enabled = True
End Sub

Private Sub Stop_Click()
Timer1.Enabled = False
Hour = 0
End Sub

Private Sub Timer1_Timer()
Hour = Hour + 1
Label2.Caption = "Seconds until next image: " & 3600 - Hour
If Hour = 3600 Then
    Hour = 0
    Dim CDT As String
    Dim CDT1 As String
    Dim CDT2 As String
    CDT = Now
    CDT1 = Replace(CDT, "/", "-")
    CDT2 = Replace(CDT1, ":", ".")
    url = "http://www.goes.noaa.gov/sohemi/sohemiloops/ircolgms/8.jpg"
    localFileName = "C:\Loops\" & CDT2 & ".jpg"
    errcode = URLDownloadToFile(0, url, localFileName, 0, 0)
    If errcode = 0 Then
    Label3.Caption = "Download Successful"
    Label1.Caption = "Last download: " & Now
    Else
    Label3.Caption = "Error Downloading"
    Label1.Caption = "Failed download: " & Now
End If
End If
End Sub

---

Regards,
Dan

Use the BINDF_GETNEWESTVERSION flag.

vb Code:

Private Const BINDF_GETNEWESTVERSION As Long = &H10
 
errcode = URLDownloadToFile(0, url, localFileName, BINDF_GETNEWESTVERSION, 0)

Well, that's odd, it still downloaded the same image twice :(

Code:

---

Dim Hour As Integer

Private Declare Function URLDownloadToFile Lib "urlmon" Alias _
    "URLDownloadToFileA" (ByVal pCaller As Long, ByVal szURL As String, _
    ByVal szFileName As String, ByVal dwReserved As Long, _
    ByVal lpfnCB As Long) As Long
   
Dim errcode As Long
Dim url As String
Dim localFileName As String
Private Const BINDF_GETNEWESTVERSION As Long = &H10



Private Sub StartBtn_Click()
    Dim CDT As String
    Dim CDT1 As String
    Dim CDT2 As String
    CDT = Now
    CDT1 = Replace(CDT, "/", "-")
    CDT2 = Replace(CDT1, ":", ".")
    url = "http://www.goes.noaa.gov/sohemi/sohemiloops/ircolgms/8.jpg"
    localFileName = "C:\Loops\" & CDT2 & ".jpg"
    errcode = URLDownloadToFile(0, url, localFileName, BINDF_GETNEWESTVERSION, 0)
    If errcode = 0 Then
    Label3.Caption = "Download Successful"
    Label1.Caption = "Last download: " & Now
    Else
    Label3.Caption = "Error Downloading"
    Label1.Caption = "Failed download: " & Now
End If
Timer1.Enabled = True
End Sub

Private Sub Stop_Click()
Timer1.Enabled = False
Hour = 0
End Sub

Private Sub Timer1_Timer()
Hour = Hour + 1
Label2.Caption = "Seconds until next image: " & 3600 - Hour
If Hour = 3600 Then
    Hour = 0
    Dim CDT As String
    Dim CDT1 As String
    Dim CDT2 As String
    CDT = Now
    CDT1 = Replace(CDT, "/", "-")
    CDT2 = Replace(CDT1, ":", ".")
    url = "http://www.goes.noaa.gov/sohemi/sohemiloops/ircolgms/8.jpg"
    localFileName = "C:\Loops\" & CDT2 & ".jpg"
    errcode = URLDownloadToFile(0, url, localFileName, BINDF_GETNEWESTVERSION, 0)
    If errcode = 0 Then
    Label3.Caption = "Download Successful"
    Label1.Caption = "Last download: " & Now
    Else
    Label3.Caption = "Error Downloading"
    Label1.Caption = "Failed download: " & Now
End If
End If
End Sub

---

Regards,
Dan

I don't use that API function, but any official documentation I can find on MSDN indicates BINDF_GETNEWESTVERSION is not used with URLDownloadToFile but with URLDownloadToCacheFile instead.

The "command2" example at this link, clears the cache first then downloads the target. Note that example is also using BINDF_GETNEWESTVERSION & maybe improperly.

Hmm, I tested BINDF_GETNEWESTVERSION with URLDownloadToFile a while ago and it worked fine.

It is also used on vbnet.mvps.org.

http://vbnet.mvps.org/index.html?cod...loadtofile.htm

Hmm, seems to be working now. Looks like it only saves duplicates of the first 2 images.

Cheers,
Dan

i had a similar problem downloading updated vb6 exe, using firefox
so i made a small app using urldownloadtofile, to clear cache and always download the new version of exe
worked fine for me