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VB.NET-APP Downloading file using httpwebrequest/response

59 New Member
Hello, i have a program that downloads a file using the httpwebrequest/response, and it usually works, but sometimes it will freeze at a random part of the download without an error.
here is the code:
Expand|Select|Wrap|Line Numbers
  1.   'Creating the request and getting the response
  2.         Dim theResponse As HttpWebResponse
  3.         Dim theRequest As HttpWebRequest
  5.         Try 'Checks if the file exist
  6.             theRequest = WebRequest.Create(Me.Filelocation)
  7.             theResponse = theRequest.GetResponse
  8.         Catch ex As Exception
  10.             MessageBox.Show("An error occurred while downloading file. Possibe causes:" & ControlChars.CrLf & _
  11.                             "1) File doesn't exist" & ControlChars.CrLf & _
  12.                             "2) Remote server error", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
  14.             Dim cancelDelegate As New DownloadCompleteSafe(AddressOf DownloadComplete)
  16.             Me.Invoke(cancelDelegate, True)
  18.             Exit Sub
  19.         End Try
  20.         theRequest.Timeout = 30000
  21.         theRequest.KeepAlive = True
  22.         Dim length As Long = theResponse.ContentLength 'Size of the response (in bytes)
  24.         Dim safedelegate As New ChangeTextsSafe(AddressOf ChangeTexts)
  25.         Me.Invoke(safedelegate, length, 0, 0, 0) 'Invoke the TreadsafeDelegate
  27.         Dim writeStream As New IO.FileStream(Me.whereToSave, IO.FileMode.Create)
  29.         'Replacement for Stream.Position (webResponse stream doesn't support seek)
  30.         Dim nRead As Integer
  32.         'To calculate the download speed
  33.         Dim speedtimer As New Stopwatch
  34.         Dim currentspeed As Double = -1
  35.         Dim readings As Integer = 0
  37.         Do
  38.             If BackgroundWorker1.CancellationPending Then 'If user abort download
  39.                 Exit Do
  40.             End If
  42.             speedtimer.Start()
  44.             Dim readBytes(4095) As Byte
  45.             Dim bytesread As Integer = theResponse.GetResponseStream.Read(readBytes, 0, 4096)
  47.             nRead += bytesread
  48.             Dim percent As Integer = (nRead / length) * 100
  50.             Me.Invoke(safedelegate, length, nRead, percent, currentspeed)
  52.             If bytesread = 0 Then Exit Do
  54.             writeStream.Write(readBytes, 0, bytesread)
  56.             speedtimer.Stop()
  58.             readings += 1
  59.             If readings >= 5 Then 'For increase precision, the speed it's calculated only every five cicles
  60.                 currentspeed = 20480 / (speedtimer.ElapsedMilliseconds / 1000)
  61.                 speedtimer.Reset()
  62.                 readings = 0
  63.             End If
  64.         Loop
  66.         'Close the streams
  67.         theResponse.GetResponseStream.Close()
  68.         writeStream.Close()
  70.         If Me.BackgroundWorker1.CancellationPending Then
  72.             IO.File.Delete(Me.whereToSave)
  74.             Dim cancelDelegate As New DownloadCompleteSafe(AddressOf DownloadComplete)
  76.             Me.Invoke(cancelDelegate, True)
  78.             Exit Sub
  80.         End If
  82.         Dim completeDelegate As New DownloadCompleteSafe(AddressOf DownloadComplete)
  83.         Try
  84.             Me.Invoke(completeDelegate, False)
  85.         Catch ex As Exception
  86.             MsgBox(ex.Message)
  87.         End Try
But im pretty sure my problem is in this part of the code:

Expand|Select|Wrap|Line Numbers
  2.  Do
  3.  If BackgroundWorker1.CancellationPending Then 'If user abort download
  4.                 Exit Do
  5.             End If
  7.             speedtimer.Start()
  9.             Dim readBytes(4095) As Byte
  10.             Dim bytesread As Integer = theResponse.GetResponseStream.Read(readBytes, 0, 4096)
  12.             nRead += bytesread
  13.             Dim percent As Integer = (nRead / length) * 100
  15.             Me.Invoke(safedelegate, length, nRead, percent, currentspeed)
  17.             If bytesread = 0 Then Exit Do
  19.             writeStream.Write(readBytes, 0, bytesread)
  21.             speedtimer.Stop()
  23.             readings += 1
  24.             If readings >= 5 Then 'For increase precision, the speed it's calculated only every five cicles
  25.                 currentspeed = 20480 / (speedtimer.ElapsedMilliseconds / 1000)
  26.                 speedtimer.Reset()
  27.                 readings = 0
  28.             End If
  29.         Loop
Nov 9 '08 #1
7 7794
583 Contributor
Put a Try...Catch Statement around the WHOLE code, and then in the 'Catch Ex as Exception' line, under that have a message box showing the whole error.


Expand|Select|Wrap|Line Numbers
  1.       Try
  2.         'All Code
  3.         Catch ex As Exception
  4.             MessageBox.Show(ex.ToString())
  5.         End Try
This should give you an error the error that's happening some point in the code, post back the error and line number so we can help you furthermore. :)

Nov 9 '08 #2
59 New Member
i tried that already, but it doesnt show that anythings wrong, the whole program still works but the downloaded freezes at a random place... and it doesnt do it all the time it, its just random.
Nov 9 '08 #3
583 Contributor
Hmm...This has occurred to me a while ago when I was working with downloading files, but since you're in VB.NET, why not use the My.Computer.Net work.DownloadFi le() Method, it's kind of the lazy way, but if it works?

Nov 10 '08 #4
59 New Member
because i want to get the speed and progress of the download
Nov 13 '08 #5
7,872 Recognized Expert Expert
Hmm these lines:
theRequest.Time out = 30000
theRequest.Keep Alive = True
have no effect since you have already called for the response.

Your code does lot of work, is it possible it is getting stuck in a loop somewhere.
Have you set a breakpoint and stepped through your code?
Nov 13 '08 #6
59 New Member
its usually just a random point that it just decides to stop downloading, i did find a quick fix though... instead of using a backgroundworke r i just put it all in a different sub and called application.doe vents, and this seemed to fix it.
Dec 2 '08 #7
7,872 Recognized Expert Expert
That was as I thought.
You are in a busy loop somewhere trying to get the rest of the data, but the managed object doesn't know more data has come in, because it never had the chance to get its messages (the doevents() call)
Dec 2 '08 #8

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