(Java) Restart/Resume FTP Download

Resume downloading a file from an FTP server.

Chilkat Java Downloads Java Libs for Windows, MacOS, Linux, Alpine Linux Java Libs for Android

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[])
  {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkFtp2 ftp = new CkFtp2();

    ftp.put_Hostname("ftp.example.com");
    ftp.put_Username("login");
    ftp.put_Password("password");

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

    // Change to the remote directory where the file is located.
    // This step is only necessary if the file is not in the root directory
    // for the FTP account.
    success = ftp.ChangeRemoteDir("temp");
    if (success != true) {
        System.out.println(ftp.lastErrorText());
        return;
        }

    // To resume a download, it is assumed that the partial file
    // is already present on the local filesystem.
    // You only need to set the RestartNext property to resume
    // the download.  The Chilkat FTP component sets the resume
    // point by getting the existing size of the target (local) file.
    ftp.put_RestartNext(true);

    String localFilename = "big.zip";
    String remoteFilename = "big.zip";

    // Resume downloading...
    success = ftp.GetFile(remoteFilename,localFilename);
    if (success != true) {
        System.out.println(ftp.lastErrorText());
        return;
        }

    success = ftp.Disconnect();

    System.out.println("File Downloaded!");
  }
}