Xojo Plugin

Monitor, Cancel, and Keep-Alive Long FTP Transfers

Demonstrates the HeartbeatMs, AbortCurrent, and LargeFileMeasures properties, which monitor long operations, allow cancellation, and keep the control connection alive during long transfers.

Note: The local paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: A large transfer blocks for a long time, and these properties make that manageable. HeartbeatMs fires a periodic AbortCheck callback so an application can show progress and remain responsive, and AbortCurrent — set from that callback or another thread — cancels the running operation. LargeFileMeasures addresses a subtler problem: while data flows on the data connection, an idle control connection can be dropped by a firewall, so this sends a periodic NOOP to keep it alive.

Chilkat Xojo Plugin Downloads

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Xojo Plugin

Dim success As Boolean
success = False

Dim ftp As New Chilkat.Ftp2

ftp.Hostname = "ftp.example.com"
ftp.Username = "myFtpLogin"

//  Normally you would not hard-code the password in source.  You should instead obtain it
//  from an interactive prompt, environment variable, or a secrets vault.
ftp.Password = "myPassword"

//  HeartbeatMs sets how often the AbortCheck event fires during long operations.  The default 0
//  disables it.  A nonzero value lets an application monitor progress and request cancellation.
ftp.HeartbeatMs = 100

//  AbortCurrent may be set to 1 (typically from another thread, or from an AbortCheck
//  callback) to cancel a running operation.  Left 0 here so nothing is pre-emptively aborted.
ftp.AbortCurrent = False

//  LargeFileMeasures (default 0) sends a NOOP on the control channel once per minute during
//  a long transfer, keeping the control connection alive while data flows.
ftp.LargeFileMeasures = True

success = ftp.Connect()
If (success = False) Then
    System.DebugLog(ftp.LastErrorText)
    Return
End If

success = ftp.GetFile("public_html/hugefile.iso","qa_output/hugefile.iso")
If (success = False) Then
    System.DebugLog(ftp.LastErrorText)
    Return
End If

System.DebugLog("Transfer complete.")

success = ftp.Disconnect()
If (success = False) Then
    System.DebugLog(ftp.LastErrorText)
    Return
End If