(VB.NET) Async FTP Progress Info

Demonstrates checking for progress info updates when running a task asynchronously. This example demonstrates an FTP download.

Chilkat .NET Downloads Chilkat .NET Framework Chilkat for .NET Core

' This example assumes the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.


Dim ftp As New Chilkat.Ftp2

ftp.Hostname = "ftp.someFtpServer.com"
Dim success As Boolean = ftp.ConnectOnly()
If (success <> True) Then
    Debug.WriteLine(ftp.LastErrorText)
    Exit Sub
End If


ftp.Username = "myLogin"
ftp.Password = "myPassword"
success = ftp.LoginAfterConnectOnly()
If (success <> True) Then
    Debug.WriteLine(ftp.LastErrorText)
    Exit Sub
End If




' Change to the remote directory where the file is located.
' This step is only necessary if the file is not in the root directory
' for the FTP account.
success = ftp.ChangeRemoteDir("someRemoteDirectory")
If (success <> True) Then
    Debug.WriteLine(ftp.LastErrorText)
    Exit Sub
End If


Dim localFilename As String = "/temp/romeo.xml"
Dim remoteFilename As String = "romeo.xml"


' --------------------
' Download a file
' --------------------

' Call the async version of the GetFile method to return a task object.
' The task object is loaded, but is in the Inert state -- meaning it is
' not yet scheduled to run on Chilkat's background thread pool.
Dim task As Chilkat.Task = ftp.GetFileAsync(remoteFilename,localFilename)
If (ftp.LastMethodSuccess = False) Then
    Debug.WriteLine(ftp.LastErrorText)
    Exit Sub
End If


' Before starting the task, tell it to keep an in-memory log of what would've been
' ProgressInfo callbacks.
task.KeepProgressLog = True

' Schedule the task for running on the thread pool.  This changes the task's state
' from Inert to Live.
success = task.Run()
If (success <> True) Then
    Debug.WriteLine(task.LastErrorText)

    Exit Sub
End If


' The application is now free to do anything else
' while the file is being downloaded.

' For this example, we'll simply sleep and periodically
' check to see if the download is finished, and report the progress
' along the way.
Dim curPctDone As Integer = 0
Dim name As String
Dim value As String

While task.Finished <> True

    If (task.PercentDone <> curPctDone) Then
        curPctDone = task.PercentDone
        Debug.WriteLine(curPctDone & " percent done")
    End If


    ' Check the progress info log.
    ' Emit any log entries..
    While (task.ProgressLogSize > 0)
        ' Get the 1st entry, emit it, and then remove it..
        name = task.ProgressInfoName(0)
        value = task.ProgressInfoValue(0)

        ' Entries reporting the received byte count will have the name "RcvByteCount"
        ' Entries reporting the current bytes-per-second will have the name "RcvBytesPerSec"

        Debug.WriteLine(name & ": " & value)
        task.RemoveProgressInfo(0)
    End While

    ' Sleep 100 ms.
    task.SleepMs(100)

End While

' Just in case there are any remaining entries...
While (task.ProgressLogSize > 0)
    ' Get the 1st entry, emit it, and then remove it..
    name = task.ProgressInfoName(0)
    value = task.ProgressInfoValue(0)
    Debug.WriteLine(name & ": " & value)
    task.RemoveProgressInfo(0)
End While


' A finished task could be one that was canceled, aborted, or truly finished.  

' If the task was "canceled", it was canceled prior to actually starting.  This could
' happen if the task was canceled while waiting in a thread pool queue to be scheduled by Chilkat's
' background thread pool scheduler.  

' If the task was "aborted", it indicates that it was canceled while running in a background thread.  
' The ResultErrorText will likely indicate that the task was aborted.

' If the task "completed", then it ran to completion, but the actual success/failure of the method
' is determined by the result obtained via a GetResult* method.  (A "completed" task will
' have a StatusInt equal to 7.   If the task finished, but was not completed, then it must've
' been aborted or canceled:
If (task.StatusInt <> 7) Then
    Debug.WriteLine("Task did not complete.")
    Debug.WriteLine("task status: " & task.Status)

    Exit Sub
End If


' The GetFile method returns a boolean.  Therefore, after the task is finished,
' we can get the boolean result by calling GetResultBool.  This is the return value had
' we called GetFile synchronously.
success = task.GetResultBool()
If (success <> True) Then
    ' The task's ResultErrorText contains what would have been in the LastErrorText property had
    ' the GetFile method been called synchronously.
    Debug.WriteLine(task.ResultErrorText)
Else
    Debug.WriteLine("File downloaded asynchronously.")
End If




success = ftp.Disconnect()