(VB.NET) Asynchronous FTP Download

The Chilkat FTP component supports asynchronous uploads and downloads. This examples demonstrates doing a download in a background thread. The download is started by calling AsyncGetFileStart. While the download is in progress, your program may do other tasks. You may periodically check the AsyncFinished property to determine when the transfer is finished. The example below provides the remainder of the details.

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Dim ftp As New Chilkat.Ftp2()

Dim success As Boolean

'  Any string unlocks the component for the 1st 30-days.
success = ftp.UnlockComponent("Anything for 30-day trial")
If (success <> true) Then
    MsgBox(ftp.LastErrorText)
    Exit Sub
End If


ftp.Hostname = "www.secureftp-test.com"
ftp.Username = "test"
ftp.Password = "test"


'  Connect and login to the FTP server.
success = ftp.Connect()
If (success <> true) Then
    MsgBox(ftp.LastErrorText)
    Exit Sub
End If


Dim localFilename As String
localFilename = "hamlet.xml"
Dim remoteFilename As String
remoteFilename = "hamlet.xml"

'  Begin the download in a background thread.
'  Only 1 background upload or download may be active at any time.
'  (per instance of an FTP object)
success = ftp.AsyncGetFileStart(remoteFilename,localFilename)
If (success <> true) Then
    MsgBox(ftp.LastErrorText)
    Exit Sub
End If


'  The application is now free to do anything else
'  while the file is downloading.
'  For this example, we'll simply sleep and periodically
'  check to see if the transfer if finished.  While checking
'  however, we'll report on the progress in both number
'  of bytes tranferred and performance in bytes/second.
While ftp.AsyncFinished <> true

    TextBox1.Text = TextBox1.Text & ftp.AsyncBytesReceived _
         & " bytes received" & vbCrLf
    TextBox1.Text = TextBox1.Text & ftp.DownloadRate _
         & " bytes per second" & vbCrLf

    '  Sleep 1 second.
    ftp.SleepMs(1000)

End While
TextBox1.Text = TextBox1.Text & ftp.AsyncBytesReceived _
     & " total bytes received" & vbCrLf
TextBox1.Text = TextBox1.Text & ftp.DownloadRate _
     & " final bytes per second" & vbCrLf

'  Did the download succeed?
If (ftp.AsyncSuccess = true) Then
    MsgBox("File Downloaded!")
Else
    '  The error information for asynchronous ops
    '  is in AsyncLog as opposed to LastErrorText
    MsgBox(ftp.AsyncLog)
End If


ftp.Disconnect()