WSAECONNRESET An existing connection was forcibly closed by the remote host.

Explains the meaning of the "WSAECONNRESET An existing connection was forcibly closed by the remote host." error and demonstrates a way to reproduce it by setting the "No Transfer Timeout" setting on a FileZilla FTP server to a very small value.

 Chilkat Java Library Downloads for Windows, Linux, and MAC OS X

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("192.168.1.108");
    ftp.put_Username("myLogin");
    ftp.put_Password("myPassword");

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

    ftp.put_Passive(true);

    //  In this example, we've set the FileZilla FTP Server's
    //  "No Transfer Timeout" to 5 seconds.  This is a setting
    //  on the FTP server (not in the Chilkat FTP component).
    //  It causes the server to disconnect from the client after
    //  5 seconds of no upload or download activity.  As you'll see,
    //  sending commands over the control channel, such as
    //  NOOP (no-operation) commands will have no effect.
    //  It is an upload, download, or directory listing that is required.

    //  This code will wait 10 seconds before proceeding with
    //  the PutFile.  This should be enough time for the FileZilla
    //  server to disconnect.
    int i;
    for (i = 0; i <= 10; i++) {
        //  Sleep for 1 second
        ftp.SleepMs(1000);

        //  Send a NOOP command to the FTP server.
        //  After about 5 iterations, it should fail and the LastErrorText
        //  will contain this message:
        //  WSAECONNRESET An existing connection was forcibly closed by the remote host.
        success = ftp.Noop();
        if (success != true) {
            System.out.println(ftp.lastErrorText());
            break;
        }

    }

    //  What happens if we try to upload a file without an existing
    //  connection?
    //  Let's do it and find out...

    //  Upload a file.
    String localFilename;
    localFilename = "c:/temp/hamlet.xml";
    String remoteFilename;
    remoteFilename = "hamlet.xml";

    success = ftp.PutFile(localFilename,remoteFilename);
    if (success != true) {

        //  In Active mode (i.e. non-passive), we get this error:
        //  "Failed to get socket's IP address. Socket may already be disconnected."
        //  In Passive mode, we'll get this error:
        //  " No socket exists for sending (2)"
        System.out.println(ftp.lastErrorText());
        return;
    }

    ftp.Disconnect();

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