PureBasic

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.

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PureBasic

IncludeFile "CkFtp2.pb"

Procedure ChilkatExample()

    success.i = 0

    ftp.i = CkFtp2::ckCreate()
    If ftp.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkFtp2::setCkHostname(ftp, "ftp.example.com")
    CkFtp2::setCkUsername(ftp, "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.
    CkFtp2::setCkPassword(ftp, "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.
    CkFtp2::setCkHeartbeatMs(ftp, 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.
    CkFtp2::setCkAbortCurrent(ftp, 0)

    ;  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.
    CkFtp2::setCkLargeFileMeasures(ftp, 1)

    success = CkFtp2::ckConnect(ftp)
    If success = 0
        Debug CkFtp2::ckLastErrorText(ftp)
        CkFtp2::ckDispose(ftp)
        ProcedureReturn
    EndIf

    success = CkFtp2::ckGetFile(ftp,"public_html/hugefile.iso","qa_output/hugefile.iso")
    If success = 0
        Debug CkFtp2::ckLastErrorText(ftp)
        CkFtp2::ckDispose(ftp)
        ProcedureReturn
    EndIf

    Debug "Transfer complete."

    success = CkFtp2::ckDisconnect(ftp)
    If success = 0
        Debug CkFtp2::ckLastErrorText(ftp)
        CkFtp2::ckDispose(ftp)
        ProcedureReturn
    EndIf



    CkFtp2::ckDispose(ftp)


    ProcedureReturn
EndProcedure