Swift

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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Swift


func chilkatTest() {
    var success: Bool = false

    let ftp = CkoFtp2()!

    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"

    success = ftp.connect()
    if success == false {
        print("\(ftp.lastErrorText!)")
        return
    }

    //  RestartNext requests that the NEXT transfer resume from existing content rather than starting
    //  over.  It is consumed by that transfer and then automatically reset.
    ftp.restartNext = true

    //  Resume a partially-downloaded file.  Because RestartNext is set, the download continues from
    //  the current local file size.
    success = ftp.getFile(remoteFilename: "public_html/bigfile.zip", localPath: "qa_output/bigfile.zip")
    if success == false {
        print("\(ftp.lastErrorText!)")
        return
    }

    //  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 ftp.partialTransfer {
        print("Only part of the file was received; another resume may be needed.")
    }
    else {
        print("The file was fully received.")
    }

    success = ftp.disconnect()
    if success == false {
        print("\(ftp.lastErrorText!)")
        return
    }


}