Java

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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Java

import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    boolean success = false;

    CkFtp2 ftp = new CkFtp2();

    ftp.put_Hostname("ftp.example.com");
    ftp.put_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.put_Password("myPassword");

    success = ftp.Connect();
    if (success == false) {
        System.out.println(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.put_RestartNext(true);

    //  Resume a partially-downloaded file.  Because RestartNext is set, the download continues from
    //  the current local file size.
    success = ftp.GetFile("public_html/bigfile.zip","qa_output/bigfile.zip");
    if (success == false) {
        System.out.println(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.get_PartialTransfer()) {
        System.out.println("Only part of the file was received; another resume may be needed.");
        }
    else {
        System.out.println("The file was fully received.");
        }

    success = ftp.Disconnect();
    if (success == false) {
        System.out.println(ftp.lastErrorText());
        return;
        }
  }
}