Asynchronous FTP Download

The Chilkat FTP component supports asynchronous uploads and downloads. This examples demonstrates doing a download in a background thread. The download is started by calling AsyncGetFileStart. While the download is in progress, your program may do other tasks. You may periodically check the AsyncFinished property to determine when the transfer is finished. The example below provides the remainder of the details.

Download Chilkat Java Library

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[])
  {
    CkFtp2 ftp = new CkFtp2();

    boolean success;

    //  Any string unlocks the component for the 1st 30-days.
    success = ftp.UnlockComponent("Anything for 30-day trial");
    if (success != true) {
        System.out.println(ftp.lastErrorText());
        return;
    }

    ftp.put_Hostname("www.secureftp-test.com");
    ftp.put_Username("test");
    ftp.put_Password("test");

    //  Connect and login to the FTP server.
    success = ftp.Connect();
    if (success != true) {
        System.out.println(ftp.lastErrorText());
        return;
    }

    String localFilename;
    localFilename = "hamlet.xml";
    String remoteFilename;
    remoteFilename = "hamlet.xml";

    //  Begin the download in a background thread.
    //  Only 1 background upload or download may be active at any time.
    //  (per instance of an FTP object)
    success = ftp.AsyncGetFileStart(remoteFilename,localFilename);
    if (success != true) {
        System.out.println(ftp.lastErrorText());
        return;
    }

    //  The application is now free to do anything else
    //  while the file is downloading.
    //  For this example, we'll simply sleep and periodically
    //  check to see if the transfer if finished.  While checking
    //  however, we'll report on the progress in both number
    //  of bytes tranferred and performance in bytes/second.
    while (ftp.get_AsyncFinished() != true) {

        System.out.println(ftp.get_AsyncBytesReceived()
             + " bytes received");
        System.out.println(ftp.get_DownloadRate()
             + " bytes per second");

        //  Sleep 1 second.
        ftp.SleepMs(1000);
    }

    //  Did the download succeed?
    if (ftp.get_AsyncSuccess() == true) {
        System.out.println("File Downloaded!");
    }
    else {
        //  The error information for asynchronous ops
        //  is in AsyncLog as opposed to LastErrorText
        System.out.println(ftp.asyncLog());
    }

    ftp.Disconnect();
  }
}