VB.NET-APP Downloading file using httpwebrequest/response

[raids51]

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:

  'Creating the request and getting the response
        Dim theResponse As HttpWebResponse
        Dim theRequest As HttpWebRequest
 
        Try 'Checks if the file exist
            theRequest = WebRequest.Create(Me.Filelocation)
            theResponse = theRequest.GetResponse
        Catch ex As Exception
 
            MessageBox.Show("An error occurred while downloading file. Possibe causes:" & ControlChars.CrLf & _
                            "1) File doesn't exist" & ControlChars.CrLf & _
                            "2) Remote server error", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
 
            Dim cancelDelegate As New DownloadCompleteSafe(AddressOf DownloadComplete)
 
            Me.Invoke(cancelDelegate, True)
 
            Exit Sub
        End Try
        theRequest.Timeout = 30000
        theRequest.KeepAlive = True
        Dim length As Long = theResponse.ContentLength 'Size of the response (in bytes)
 
        Dim safedelegate As New ChangeTextsSafe(AddressOf ChangeTexts)
        Me.Invoke(safedelegate, length, 0, 0, 0) 'Invoke the TreadsafeDelegate
 
        Dim writeStream As New IO.FileStream(Me.whereToSave, IO.FileMode.Create)
 
        'Replacement for Stream.Position (webResponse stream doesn't support seek)
        Dim nRead As Integer
 
        'To calculate the download speed
        Dim speedtimer As New Stopwatch
        Dim currentspeed As Double = -1
        Dim readings As Integer = 0
 
        Do
            If BackgroundWorker1.CancellationPending Then 'If user abort download
                Exit Do
            End If
 
            speedtimer.Start()
 
            Dim readBytes(4095) As Byte
            Dim bytesread As Integer = theResponse.GetResponseStream.Read(readBytes, 0, 4096)
 
            nRead += bytesread
            Dim percent As Integer = (nRead / length) * 100
 
            Me.Invoke(safedelegate, length, nRead, percent, currentspeed)
 
            If bytesread = 0 Then Exit Do
 
            writeStream.Write(readBytes, 0, bytesread)
 
            speedtimer.Stop()
 
            readings += 1
            If readings >= 5 Then 'For increase precision, the speed it's calculated only every five cicles
                currentspeed = 20480 / (speedtimer.ElapsedMilliseconds / 1000)
                speedtimer.Reset()
                readings = 0
            End If
        Loop
 
        'Close the streams
        theResponse.GetResponseStream.Close()
        writeStream.Close()
 
        If Me.BackgroundWorker1.CancellationPending Then
 
            IO.File.Delete(Me.whereToSave)
 
            Dim cancelDelegate As New DownloadCompleteSafe(AddressOf DownloadComplete)
 
            Me.Invoke(cancelDelegate, True)
 
            Exit Sub
 
        End If
 
        Dim completeDelegate As New DownloadCompleteSafe(AddressOf DownloadComplete)
        Try
            Me.Invoke(completeDelegate, False)
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try

But im pretty sure my problem is in this part of the code:

 
 Do
 If BackgroundWorker1.CancellationPending Then 'If user abort download
                Exit Do
            End If
 
            speedtimer.Start()
 
            Dim readBytes(4095) As Byte
            Dim bytesread As Integer = theResponse.GetResponseStream.Read(readBytes, 0, 4096)
 
            nRead += bytesread
            Dim percent As Integer = (nRead / length) * 100
 
            Me.Invoke(safedelegate, length, nRead, percent, currentspeed)
 
            If bytesread = 0 Then Exit Do
 
            writeStream.Write(readBytes, 0, bytesread)
 
            speedtimer.Stop()
 
            readings += 1
            If readings >= 5 Then 'For increase precision, the speed it's calculated only every five cicles
                currentspeed = 20480 / (speedtimer.ElapsedMilliseconds / 1000)
                speedtimer.Reset()
                readings = 0
            End If
        Loop

[joedeene]

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.

Example:

      Try
        'All Code
        Catch ex As Exception
            MessageBox.Show(ex.ToString())
        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. :)

joedeene

[raids51]

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.

[joedeene]

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.Network.DownloadFile() Method, it's kind of the lazy way, but if it works?

joedeene

[raids51]

because i want to get the speed and progress of the download

[Plater]

Hmm these lines:
theRequest.Timeout = 30000
theRequest.KeepAlive = 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?

[raids51]

its usually just a random point that it just decides to stop downloading, i did find a quick fix though... instead of using a backgroundworker i just put it all in a different sub and called application.doevents, and this seemed to fix it.

[Plater]

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)