PureBasic

Resume an Interrupted FTP Transfer

Demonstrates the RestartNext and PartialTransfer properties, which request that the next transfer resume from existing content and report whether a download was incomplete.

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: For a large transfer over a flaky link, restarting from zero after a drop is wasteful. Setting RestartNext makes the next download continue from the current local file size (and the next upload from the remote size); the flag is consumed by that one transfer and then reset. Afterward PartialTransfer tells you whether the download got only part of the file — the signal to set RestartNext again and resume once more.

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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")

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

    ;  RestartNext requests that the NEXT transfer resume from existing content rather than starting
    ;  over.  It is consumed by that transfer and then automatically reset.
    CkFtp2::setCkRestartNext(ftp, 1)

    ;  Resume a partially-downloaded file.  Because RestartNext is set, the download continues from
    ;  the current local file size.
    success = CkFtp2::ckGetFile(ftp,"public_html/bigfile.zip","qa_output/bigfile.zip")
    If success = 0
        Debug CkFtp2::ckLastErrorText(ftp)
        CkFtp2::ckDispose(ftp)
        ProcedureReturn
    EndIf

    ;  PartialTransfer indicates whether the most recent download received some, but not all, of the
    ;  remote file -- distinguishing a mid-transfer failure from other outcomes.
    If CkFtp2::ckPartialTransfer(ftp)
        Debug "Only part of the file was received; another resume may be needed."
    Else
        Debug "The file was fully received."
    EndIf

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



    CkFtp2::ckDispose(ftp)


    ProcedureReturn
EndProcedure