org.apache.commons.net.ftp.FTPConnectionClosedException: Connection closed without indication.
    at org.apache.commons.net.ftp.FTP.__getReply(FTP.java:316)
    at org.apache.commons.net.ftp.FTP.__getReply(FTP.java:292)
    at org.apache.commons.net.ftp.FTP.getReply(FTP.java:712)
    at org.apache.commons.net.ftp.FTPClient.completePendingCommand(FTPClient.java:1857)
    at org.apache.commons.net.ftp.FTPClient.initiateListParsing(FTPClient.java:3420)
    at org.apache.commons.net.ftp.FTPClient.initiateListParsing(FTPClient.java:3335)
    at org.apache.commons.net.ftp.FTPClient.listFiles(FTPClient.java:3012)
    at com.capitalone.homeloans.imaging.migration.TestFTP.execute(TestFTP.java:27)
    at com.capitalone.homeloans.imaging.migration.TestFTP.main(TestFTP.java:12)
org.apache.commons.net.ftp.FTPConnectionClosedException: Connection closed without indication.
    at org.apache.commons.net.ftp.FTP.__getReply(FTP.java:316)
    at org.apache.commons.net.ftp.FTP.__getReply(FTP.java:292)
    at org.apache.commons.net.ftp.FTP.sendCommand(FTP.java:503)
    at org.apache.commons.net.ftp.FTP.sendCommand(FTP.java:628)
    at org.apache.commons.net.ftp.FTP.sendCommand(FTP.java:602)
    at org.apache.commons.net.ftp.FTP.quit(FTP.java:884)
    at org.apache.commons.net.ftp.FTPClient.logout(FTPClient.java:1152)
    at com.capitalone.homeloans.imaging.migration.TestFTP.execute(TestFTP.java:62)
    at com.capitalone.homeloans.imaging.migration.TestFTP.main(TestFTP.java:12)

package com.capitalone.homeloans.imaging.migration;

import java.io.IOException;
import java.text.DateFormat;
import java.text.SimpleDateFormat;

import org.apache.commons.net.ftp.FTPClient;
import org.apache.commons.net.ftp.FTPFile;

public class TestFTP {
    public static void main(String[] args) {
        TestFTP.execute(args[0], args[1]);
    }
    static DateFormat dateFormater = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    public static void execute(String ip, String folder) {
        String server = ip;
        int port = 21;
        String user = "adminuser";
        String pass = "adminuser";

        long start = System.currentTimeMillis();
        FTPClient ftpClient = new FTPClient();
        try {
            ftpClient.connect(server, port);
            ftpClient.login(user, pass);

            FTPFile[] files = ftpClient.listFiles(folder);
            for (FTPFile file : files) {
                String details = file.getName();

                // renaming file
                String oldFile = folder + file.getName();
                String newFile = folder + "_X_" + file.getName();

                boolean success = ftpClient.rename(oldFile, newFile);
                if (success) {
                    System.out.println(oldFile + " was successfully renamed to: "
                            + newFile);
                } else {
                    System.out.println("Failed to rename: " + oldFile);
                }
            }

            ftpClient.logout();
            ftpClient.disconnect();

            long end = System.currentTimeMillis();
            System.out.println("time:"  +(end-start));

        } catch (IOException ex) {
            ex.printStackTrace();
        } finally {
            if (ftpClient.isConnected()) {
                try {
                    ftpClient.logout();
                    ftpClient.disconnect();
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
            }
        }
    }
}