Measuring download speed - vb.net

Question

I'm downloading a file using the following:
Dim client As WebClient = New WebClient()
client.DownloadFileAsync(New Uri("http://cachefly.cachefly.net/100mb.test"), "C:\Users\Dir\100mb.test")
The file downloads and saves into the C://Users/Dir/100mb.test, but while its downloading I would like to display the download speed in a label. How can I do this? I have read many tutorials, but most of them doesn't works or are outdated. I'm a newbie with vb.net, so I can't really write something on my own, could you give me any solutions?

Answer 1

May I suggest something different?
Imports System.Net
Public Class Form1
Private tmp = IO.Path.Combine(My.Computer.FileSystem.SpecialDirectories.Temp, "snafu.fubar")
Private Downloading As Boolean = False
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
If Downloading Then Exit Sub
Downloading = True
Dim wc As New WebClient
AddHandler wc.DownloadProgressChanged, AddressOf wc_ProgressChanged
AddHandler wc.DownloadFileCompleted, AddressOf wc_DownloadDone
wc.DownloadFileAsync(New Uri("http://cachefly.cachefly.net/100mb.test"), tmp, Stopwatch.StartNew)
End Sub
Private Sub wc_DownloadDone(sender As Object, e As System.ComponentModel.AsyncCompletedEventArgs)
Downloading = False
End Sub
Private Sub wc_ProgressChanged(sender As Object, e As DownloadProgressChangedEventArgs)
Me.Label1.Text = (e.BytesReceived / (DirectCast(e.UserState, Stopwatch).ElapsedMilliseconds / 1000.0#)).ToString("#")
End Sub
End Class
Because it makes no sense to determine the speed by the last chunk of bytes received, but instead you measure the total number of bytes and divide by the TOTAL time. Passing a stopwatch instance to the eventhandler has the advantage that it doesnt 'spoil' your class code - it''s visible only where it's needed.

Answer 2

This will give you percentage in the mean time. You could probably calculate from the percentage given a start time using DateTime.Now the speed in which it the download is taking:
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Try
Dim client As WebClient = New WebClient()
AddHandler client.DownloadProgressChanged, AddressOf ProgChanged
client.DownloadFileAsync(New Uri("http://cachefly.cachefly.net/100mb.test"), "C:\Users\Dir\100mb.test")
Catch ex As Exception
MessageBox.Show(ex.Message)
End Try
End Sub
Private Sub ProgChanged(ByVal sender As Object, ByVal e As DownloadProgressChangedEventArgs)
Dim progressPercentage As Integer = e.ProgressPercentage
End Sub

Answer 3

Define globals:
Dim lastUpdate As DateTime
Dim lastBytes As Long = 0
You'll need to assign an Event for progress:
Dim client As WebClient = New WebClient()
client.DownloadFileAsync(New Uri("http://cachefly.cachefly.net/100mb.test"), "C:\Users\Dir\100mb.test")
client.DownloadProgressChanged += Function(sender, e) progressChanged(e.BytesReceived)
The Event:
Private Sub progressChanged(bytes As Long)
If lastBytes = 0 Then
lastUpdate = DateTime.Now
lastBytes = bytes
Return
End If
Dim now = DateTime.Now
Dim timeSpan = now - lastUpdate
If Not timeSpan.Seconds = 0
Dim bytesChange = bytes - lastBytes
Dim bytesPerSecond = bytesChange / timeSpan.Seconds
lastBytes = bytes
lastUpdate = now
End If
End Sub
And you have the calculations of bytes per second.
label.Text = bytesPerSecond.ToString() + "B/s";

Answer 4

Try this:
Try this only when you're downloading through a backgroundworker
Private Sub worker_DoWork(Byval sender As Object, Byval e As DoWorkEventArgs)
Dim req As WebRequest = WebRequest.Create(downloadUrl) 'Make a request for the url of the file to be downloaded
Dim resp As WebResponse = req.GetResponse 'Ask for the response
Dim fs As New FileStream(path to download to, FileMode.CreateNew) 'Create a new FileStream that writes to the desired download path
Dim buffer(8192) As Byte 'Make a buffer
Dim downloadedsize As Long = 0
Dim downloadedTime As Long = 0
Dim dlSpeed As Long = 0
Dim currentSize As Long = 0 'Size that has been downloaded
Dim totalSize As Long = req.ContentLength 'Total size of the file that has to be downloaded
Do While currentSize < totalSize
Dim read As Integer = resp.GetResponseStream.Read(buffer, 0, 8192) 'Read the buffer from the response the WebRequest gave you
fs.Write(buffer, 0, read) 'Write to filestream that you declared at the beginning of the DoWork sub
currentSize += read
downloadedSize += read
downloadedTime += 1 'Add 1 millisecond for every cycle the While field makes
If downloadedTime = 1000 Then 'Then, if downloadedTime reaches 1000 then it will call this part
dlSpeed = (downloadedSize / TimeSpan.FromMilliseconds(downloadedTime).TotalSeconds) 'Calculate the download speed by dividing the downloadedSize by the total formatted seconds of the downloadedTime
downloadedTime = 0 'Reset downloadedTime and downloadedSize
downloadedSize = 0
End If
End While
fs.Close() 'Close the FileStream first, or the FileStream will crash.
resp.Close() 'Close the response
End Sub
Sorry for not using proper formatting, but this is a solution in itself.