/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.net.ftp;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.Inet4Address;
import java.net.Inet6Address;
import java.net.InetAddress;
import java.net.SocketException;
import java.net.SocketTimeoutException;
import java.util.ArrayList;

import org.apache.commons.net.MalformedServerReplyException;
import org.apache.commons.net.ProtocolCommandSupport;
import org.apache.commons.net.SocketClient;
import org.apache.commons.net.io.CRLFLineReader;

/***
 * FTP provides the basic the functionality necessary to implement your
 * own FTP client.  It extends org.apache.commons.net.SocketClient since
 * extending TelnetClient was causing unwanted behavior (like connections
 * that did not time out properly).
 * <p>
 * To derive the full benefits of the FTP class requires some knowledge
 * of the FTP protocol defined in RFC 959.  However, there is no reason
 * why you should have to use the FTP class.  The
 * {@link org.apache.commons.net.ftp.FTPClient} class,
 * derived from FTP,
 * implements all the functionality required of an FTP client.  The
 * FTP class is made public to provide access to various FTP constants
 * and to make it easier for adventurous programmers (or those with
 * special needs) to interact with the FTP protocol and implement their
 * own clients.  A set of methods with names corresponding to the FTP
 * command names are provided to facilitate this interaction.
 * <p>
 * You should keep in mind that the FTP server may choose to prematurely
 * close a connection if the client has been idle for longer than a
 * given time period (usually 900 seconds).  The FTP class will detect a
 * premature FTP server connection closing when it receives a
 * {@link org.apache.commons.net.ftp.FTPReply#SERVICE_NOT_AVAILABLE FTPReply.SERVICE_NOT_AVAILABLE }
 *  response to a command.
 * When that occurs, the FTP class method encountering that reply will throw
 * an {@link org.apache.commons.net.ftp.FTPConnectionClosedException}
 * .  <code>FTPConectionClosedException</code>
 * is a subclass of <code> IOException </code> and therefore need not be
 * caught separately, but if you are going to catch it separately, its
 * catch block must appear before the more general <code> IOException </code>
 * catch block.  When you encounter an
 * {@link org.apache.commons.net.ftp.FTPConnectionClosedException}
 * , you must disconnect the connection with
 * {@link #disconnect  disconnect() } to properly clean up the
 * system resources used by FTP.  Before disconnecting, you may check the
 * last reply code and text with
 * {@link #getReplyCode  getReplyCode },
 * {@link #getReplyString  getReplyString },
 * and {@link #getReplyStrings  getReplyStrings}.
 * You may avoid server disconnections while the client is idle by
 * periodicaly sending NOOP commands to the server.
 * <p>
 * Rather than list it separately for each method, we mention here that
 * every method communicating with the server and throwing an IOException
 * can also throw a
 * {@link org.apache.commons.net.MalformedServerReplyException}
 * , which is a subclass
 * of IOException.  A MalformedServerReplyException will be thrown when
 * the reply received from the server deviates enough from the protocol
 * specification that it cannot be interpreted in a useful manner despite
 * attempts to be as lenient as possible.
 * <p>
 * <p>
 * @author Rory Winston
 * @author Joseph Hindsley
 * @see FTPClient
 * @see FTPConnectionClosedException
 * @see org.apache.commons.net.MalformedServerReplyException
 * @version $Id: FTP.java 1299238 2012-03-10 17:12:28Z sebb $
 ***/

public class FTP extends SocketClient
{
    /*** The default FTP data port (20). ***/
    public static final int DEFAULT_DATA_PORT = 20;
    /*** The default FTP control port (21). ***/
    public static final int DEFAULT_PORT = 21;

    /***
     * A constant used to indicate the file(s) being transfered should
     * be treated as ASCII.  This is the default file type.  All constants
     * ending in <code>FILE_TYPE</code> are used to indicate file types.
     ***/
    public static final int ASCII_FILE_TYPE = 0;

    /***
     * A constant used to indicate the file(s) being transfered should
     * be treated as EBCDIC.  Note however that there are several different
     * EBCDIC formats.  All constants ending in <code>FILE_TYPE</code>
     * are used to indicate file types.
     ***/
    public static final int EBCDIC_FILE_TYPE = 1;


    /***
     * A constant used to indicate the file(s) being transfered should
     * be treated as a binary image, i.e., no translations should be
     * performed.  All constants ending in <code>FILE_TYPE</code> are used to
     * indicate file types.
     ***/
    public static final int BINARY_FILE_TYPE = 2;

    /***
     * A constant used to indicate the file(s) being transfered should
     * be treated as a local type.  All constants ending in
     * <code>FILE_TYPE</code> are used to indicate file types.
     ***/
    public static final int LOCAL_FILE_TYPE = 3;

    /***
     * A constant used for text files to indicate a non-print text format.
     * This is the default format.
     * All constants ending in <code>TEXT_FORMAT</code> are used to indicate
     * text formatting for text transfers (both ASCII and EBCDIC).
     ***/
    public static final int NON_PRINT_TEXT_FORMAT = 4;

    /***
     * A constant used to indicate a text file contains format vertical format
     * control characters.
     * All constants ending in <code>TEXT_FORMAT</code> are used to indicate
     * text formatting for text transfers (both ASCII and EBCDIC).
     ***/
    public static final int TELNET_TEXT_FORMAT = 5;

    /***
     * A constant used to indicate a text file contains ASA vertical format
     * control characters.
     * All constants ending in <code>TEXT_FORMAT</code> are used to indicate
     * text formatting for text transfers (both ASCII and EBCDIC).
     ***/
    public static final int CARRIAGE_CONTROL_TEXT_FORMAT = 6;

    /***
     * A constant used to indicate a file is to be treated as a continuous
     * sequence of bytes.  This is the default structure.  All constants ending
     * in <code>_STRUCTURE</code> are used to indicate file structure for
     * file transfers.
     ***/
    public static final int FILE_STRUCTURE = 7;

    /***
     * A constant used to indicate a file is to be treated as a sequence
     * of records.  All constants ending in <code>_STRUCTURE</code>
     * are used to indicate file structure for file transfers.
     ***/
    public static final int RECORD_STRUCTURE = 8;

    /***
     * A constant used to indicate a file is to be treated as a set of
     * independent indexed pages.  All constants ending in
     * <code>_STRUCTURE</code> are used to indicate file structure for file
     * transfers.
     ***/
    public static final int PAGE_STRUCTURE = 9;

    /***
     * A constant used to indicate a file is to be transfered as a stream
     * of bytes.  This is the default transfer mode.  All constants ending
     * in <code>TRANSFER_MODE</code> are used to indicate file transfer
     * modes.
     ***/
    public static final int STREAM_TRANSFER_MODE = 10;

    /***
     * A constant used to indicate a file is to be transfered as a series
     * of blocks.  All constants ending in <code>TRANSFER_MODE</code> are used
     * to indicate file transfer modes.
     ***/
    public static final int BLOCK_TRANSFER_MODE = 11;

    /***
     * A constant used to indicate a file is to be transfered as FTP
     * compressed data.  All constants ending in <code>TRANSFER_MODE</code>
     * are used to indicate file transfer modes.
     ***/
    public static final int COMPRESSED_TRANSFER_MODE = 12;

    // We have to ensure that the protocol communication is in ASCII
    // but we use ISO-8859-1 just in case 8-bit characters cross
    // the wire.
    /**
     * The default character encoding used for communicating over an
     * FTP control connection.  The default encoding is an
     * ASCII-compatible encoding.  Some FTP servers expect other
     * encodings.  You can change the encoding used by an FTP instance
     * with {@link #setControlEncoding setControlEncoding}.
     */
    public static final String DEFAULT_CONTROL_ENCODING = "ISO-8859-1";

    /** Length of the FTP reply code (3 alphanumerics) */
    public static final int REPLY_CODE_LEN = 3;

    private static final String __modes = "AEILNTCFRPSBC";

    protected int _replyCode;
    protected ArrayList<String> _replyLines;
    protected boolean _newReplyString;
    protected String _replyString;
    protected String _controlEncoding;

    /**
     * A ProtocolCommandSupport object used to manage the registering of
     * ProtocolCommandListeners and te firing of ProtocolCommandEvents.
     */
    protected ProtocolCommandSupport _commandSupport_;

    /**
     * This is used to signal whether a block of multiline responses beginning
     * with xxx must be terminated by the same numeric code xxx
     * See section 4.2 of RFC 959 for details.
     */
    protected boolean strictMultilineParsing = false;

    /**
     * Wraps SocketClient._input_ to facilitate the reading of text
     * from the FTP control connection.  Do not access the control
     * connection via SocketClient._input_.  This member starts
     * with a null value, is initialized in {@link #_connectAction_},
     * and set to null in {@link #disconnect}.
     */
    protected BufferedReader _controlInput_;

    /**
     * Wraps SocketClient._output_ to facilitate the writing of text
     * to the FTP control connection.  Do not access the control
     * connection via SocketClient._output_.  This member starts
     * with a null value, is initialized in {@link #_connectAction_},
     * and set to null in {@link #disconnect}.
     */
    protected BufferedWriter _controlOutput_;

    /***
     * The default FTP constructor.  Sets the default port to
     * <code>DEFAULT_PORT</code> and initializes internal data structures
     * for saving FTP reply information.
     ***/
    public FTP()
    {
        super();
        setDefaultPort(DEFAULT_PORT);
        _replyLines = new ArrayList<String>();
        _newReplyString = false;
        _replyString = null;
        _controlEncoding = DEFAULT_CONTROL_ENCODING;
        _commandSupport_ = new ProtocolCommandSupport(this);
    }

    // The RFC-compliant multiline termination check
    private boolean __strictCheck(String line, String code) {
        return (!(line.startsWith(code) && line.charAt(REPLY_CODE_LEN) == ' '));
    }

    // The strict check is too strong a condition because of non-conforming ftp
    // servers like ftp.funet.fi which sent 226 as the last line of a
    // 426 multi-line reply in response to ls /.  We relax the condition to
    // test that the line starts with a digit rather than starting with
    // the code.
    private boolean __lenientCheck(String line) {
        return (!(line.length() > REPLY_CODE_LEN&& line.charAt(REPLY_CODE_LEN) != '-' &&
                Character.isDigit(line.charAt(0))));
    }

    /**
     * Get the reply, and pass it to command listeners
     */
    private void __getReply()  throws IOException
    {
        __getReply(true);
    }

    /**
     * Get the reply, but don't pass it to command listeners.
     * Used for keep-alive processing only.
     * @since 3.0
     */
    protected void __getReplyNoReport()  throws IOException
    {
        __getReply(false);
    }

    private void __getReply(boolean reportReply) throws IOException
    {
        int length;

        _newReplyString = true;
        _replyLines.clear();

        String line = _controlInput_.readLine();

        if (line == null) {
            throw new FTPConnectionClosedException(
                    "Connection closed without indication.");
        }

        // In case we run into an anomaly we don't want fatal index exceptions
        // to be thrown.
        length = line.length();
        if (length < REPLY_CODE_LEN) {
            throw new MalformedServerReplyException(
                "Truncated server reply: " + line);
        }

        String code = null;
        try
        {
            code = line.substring(0, REPLY_CODE_LEN);
            _replyCode = Integer.parseInt(code);
        }
        catch (NumberFormatException e)
        {
            throw new MalformedServerReplyException(
                "Could not parse response code.\nServer Reply: " + line);
        }

        _replyLines.add(line);

        // Get extra lines if message continues.
        if (length > REPLY_CODE_LEN && line.charAt(REPLY_CODE_LEN) == '-')
        {
            do
            {
                line = _controlInput_.readLine();

                if (line == null) {
                    throw new FTPConnectionClosedException(
                        "Connection closed without indication.");
                }

                _replyLines.add(line);

                // The length() check handles problems that could arise from readLine()
                // returning too soon after encountering a naked CR or some other
                // anomaly.
            }
            while ( isStrictMultilineParsing() ? __strictCheck(line, code) : __lenientCheck(line));
        }

        fireReplyReceived(_replyCode, getReplyString());

        if (_replyCode == FTPReply.SERVICE_NOT_AVAILABLE) {
            throw new FTPConnectionClosedException("FTP response 421 received.  Server closed connection.");
        }
    }

    /**
     * Initiates control connections and gets initial reply.
     * Initializes {@link #_controlInput_} and {@link #_controlOutput_}.
     */
    @Override
    protected void _connectAction_() throws IOException
    {
        super._connectAction_(); // sets up _input_ and _output_
        _controlInput_ =
            new CRLFLineReader(new InputStreamReader(_input_, getControlEncoding()));
        _controlOutput_ =
            new BufferedWriter(new OutputStreamWriter(_output_, getControlEncoding()));
        if (connectTimeout > 0) { // NET-385
            int original = _socket_.getSoTimeout();
            _socket_.setSoTimeout(connectTimeout);
            try {
                __getReply();
                // If we received code 120, we have to fetch completion reply.
                if (FTPReply.isPositivePreliminary(_replyCode)) {
                    __getReply();
                }
            } catch (SocketTimeoutException e) {
                IOException ioe = new IOException("Timed out waiting for initial connect reply");
                ioe.initCause(e);
                throw ioe;
            } finally {
                _socket_.setSoTimeout(original);
            }
        } else {
            __getReply();
            // If we received code 120, we have to fetch completion reply.
            if (FTPReply.isPositivePreliminary(_replyCode)) {
                __getReply();
            }
        }
    }


    /**
     * Sets the character encoding used by the FTP control connection.
     * Some FTP servers require that commands be issued in a non-ASCII
     * encoding like UTF-8 so that filenames with multi-byte character
     * representations (e.g, Big 8) can be specified.
     *
     * @param encoding The new character encoding for the control connection.
     */
    public void setControlEncoding(String encoding) {
        _controlEncoding = encoding;
    }


    /**
     * @return The character encoding used to communicate over the
     * control connection.
     */
    public String getControlEncoding() {
        return _controlEncoding;
    }


    /***
     * Closes the control connection to the FTP server and sets to null
     * some internal data so that the memory may be reclaimed by the
     * garbage collector.  The reply text and code information from the
     * last command is voided so that the memory it used may be reclaimed.
     * Also sets {@link #_controlInput_} and {@link #_controlOutput_} to null.
     * <p>
     * @exception IOException If an error occurs while disconnecting.
     ***/
    @Override
    public void disconnect() throws IOException
    {
        super.disconnect();
        _controlInput_ = null;
        _controlOutput_ = null;
        _newReplyString = false;
        _replyString = null;
    }


    /***
     * Sends an FTP command to the server, waits for a reply and returns the
     * numerical response code.  After invocation, for more detailed
     * information, the actual reply text can be accessed by calling
     * {@link #getReplyString  getReplyString } or
     * {@link #getReplyStrings  getReplyStrings }.
     * <p>
     * @param command  The text representation of the  FTP command to send.
     * @param args The arguments to the FTP command.  If this parameter is
     *             set to null, then the command is sent with no argument.
     * @return The integer value of the FTP reply code returned by the server
     *         in response to the command.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int sendCommand(String command, String args) throws IOException
    {
        if (_controlOutput_ == null) {
            throw new IOException("Connection is not open");
        }

        final String message = __buildMessage(command, args);

        __send(message);

        fireCommandSent(command, message);

        __getReply();
        return _replyCode;
    }

    private String __buildMessage(String command, String args) {
        final StringBuilder __commandBuffer = new StringBuilder();

        __commandBuffer.append(command);

        if (args != null)
        {
            __commandBuffer.append(' ');
            __commandBuffer.append(args);
        }
        __commandBuffer.append(SocketClient.NETASCII_EOL);
        return __commandBuffer.toString();
    }

    private void __send(String message) throws IOException,
            FTPConnectionClosedException, SocketException {
        try{
            _controlOutput_.write(message);
            _controlOutput_.flush();
        }
        catch (SocketException e)
        {
            if (!isConnected())
            {
                throw new FTPConnectionClosedException("Connection unexpectedly closed.");
            }
            else
            {
                throw e;
            }
        }
    }

    /**
     * Send a noop and get the reply without reporting to the command listener.
     * Intended for use with keep-alive.
     *
     * @throws IOException
     * @since 3.0
     */
    protected void __noop() throws IOException {
        String msg = __buildMessage(FTPCommand.getCommand(FTPCommand.NOOP), null);
        __send(msg);
        __getReplyNoReport(); // This may timeout
    }

    /***
     * Sends an FTP command to the server, waits for a reply and returns the
     * numerical response code.  After invocation, for more detailed
     * information, the actual reply text can be accessed by calling
     * {@link #getReplyString  getReplyString } or
     * {@link #getReplyStrings  getReplyStrings }.
     * <p>
     * @param command  The FTPCommand constant corresponding to the FTP command
     *                 to send.
     * @param args The arguments to the FTP command.  If this parameter is
     *             set to null, then the command is sent with no argument.
     * @return The integer value of the FTP reply code returned by the server
     *         in response to the command.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int sendCommand(int command, String args) throws IOException
    {
        return sendCommand(FTPCommand.getCommand(command), args);
    }


    /***
     * Sends an FTP command with no arguments to the server, waits for a
     * reply and returns the numerical response code.  After invocation, for
     * more detailed information, the actual reply text can be accessed by
     * calling {@link #getReplyString  getReplyString } or
     * {@link #getReplyStrings  getReplyStrings }.
     * <p>
     * @param command  The text representation of the  FTP command to send.
     * @return The integer value of the FTP reply code returned by the server
     *         in response to the command.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int sendCommand(String command) throws IOException
    {
        return sendCommand(command, null);
    }


    /***
     * Sends an FTP command with no arguments to the server, waits for a
     * reply and returns the numerical response code.  After invocation, for
     * more detailed information, the actual reply text can be accessed by
     * calling {@link #getReplyString  getReplyString } or
     * {@link #getReplyStrings  getReplyStrings }.
     * <p>
     * @param command  The FTPCommand constant corresponding to the FTP command
     *                 to send.
     * @return The integer value of the FTP reply code returned by the server
     *         in response to the command.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int sendCommand(int command) throws IOException
    {
        return sendCommand(command, null);
    }


    /***
     * Returns the integer value of the reply code of the last FTP reply.
     * You will usually only use this method after you connect to the
     * FTP server to check that the connection was successful since
     * <code> connect </code> is of type void.
     * <p>
     * @return The integer value of the reply code of the last FTP reply.
     ***/
    public int getReplyCode()
    {
        return _replyCode;
    }

    /***
     * Fetches a reply from the FTP server and returns the integer reply
     * code.  After calling this method, the actual reply text can be accessed
     * from either  calling {@link #getReplyString  getReplyString } or
     * {@link #getReplyStrings  getReplyStrings }.  Only use this
     * method if you are implementing your own FTP client or if you need to
     * fetch a secondary response from the FTP server.
     * <p>
     * @return The integer value of the reply code of the fetched FTP reply.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while receiving the
     *                         server reply.
     ***/
    public int getReply() throws IOException
    {
        __getReply();
        return _replyCode;
    }


    /***
     * Returns the lines of text from the last FTP server response as an array
     * of strings, one entry per line.  The end of line markers of each are
     * stripped from each line.
     * <p>
     * @return The lines of text from the last FTP response as an array.
     ***/
    public String[] getReplyStrings()
    {
        return _replyLines.toArray(new String[_replyLines.size()]);
    }

    /***
     * Returns the entire text of the last FTP server response exactly
     * as it was received, including all end of line markers in NETASCII
     * format.
     * <p>
     * @return The entire text from the last FTP response as a String.
     ***/
    public String getReplyString()
    {
        StringBuilder buffer;

        if (!_newReplyString) {
            return _replyString;
        }

        buffer = new StringBuilder(256);

        for (String line : _replyLines) {
                buffer.append(line);
                buffer.append(SocketClient.NETASCII_EOL);
        }

         _newReplyString = false;

        return (_replyString = buffer.toString());
    }


    /***
     * A convenience method to send the FTP USER command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @param username  The username to login under.
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int user(String username) throws IOException
    {
        return sendCommand(FTPCommand.USER, username);
    }

    /**
     * A convenience method to send the FTP PASS command to the server,
     * receive the reply, and return the reply code.
     * @param password The plain text password of the username being logged into.
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     */
    public int pass(String password) throws IOException
    {
        return sendCommand(FTPCommand.PASS, password);
    }

    /***
     * A convenience method to send the FTP ACCT command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @param account  The account name to access.
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int acct(String account) throws IOException
    {
        return sendCommand(FTPCommand.ACCT, account);
    }


    /***
     * A convenience method to send the FTP ABOR command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int abor() throws IOException
    {
        return sendCommand(FTPCommand.ABOR);
    }

    /***
     * A convenience method to send the FTP CWD command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @param directory The new working directory.
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int cwd(String directory) throws IOException
    {
        return sendCommand(FTPCommand.CWD, directory);
    }

    /***
     * A convenience method to send the FTP CDUP command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int cdup() throws IOException
    {
        return sendCommand(FTPCommand.CDUP);
    }

    /***
     * A convenience method to send the FTP QUIT command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int quit() throws IOException
    {
        return sendCommand(FTPCommand.QUIT);
    }

    /***
     * A convenience method to send the FTP REIN command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int rein() throws IOException
    {
        return sendCommand(FTPCommand.REIN);
    }

    /***
     * A convenience method to send the FTP SMNT command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @param dir  The directory name.
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int smnt(String dir) throws IOException
    {
        return sendCommand(FTPCommand.SMNT, dir);
    }

    /***
     * A convenience method to send the FTP PORT command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @param host  The host owning the port.
     * @param port  The new port.
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int port(InetAddress host, int port) throws IOException
    {
        int num;
        StringBuilder info = new StringBuilder(24);

        info.append(host.getHostAddress().replace('.', ','));
        num = port >>> 8;
        info.append(',');
        info.append(num);
        info.append(',');
        num = port & 0xff;
        info.append(num);

        return sendCommand(FTPCommand.PORT, info.toString());
    }

    /***
     * A convenience method to send the FTP EPRT command to the server,
     * receive the reply, and return the reply code.
     *
     * Examples:
     * <code>
     * <ul>
     * <li>EPRT |1|132.235.1.2|6275|</li>
     * <li>EPRT |2|1080::8:800:200C:417A|5282|</li>
     * </ul>
     * </code>
     * <p>
     * @see "http://www.faqs.org/rfcs/rfc2428.html"
     *
     * @param host  The host owning the port.
     * @param port  The new port.
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     * @since 2.2
     ***/
    public int eprt(InetAddress host, int port) throws IOException
    {
        int num;
        StringBuilder info = new StringBuilder();
        String h;

        // If IPv6, trim the zone index
        h = host.getHostAddress();
        num = h.indexOf("%");
        if (num > 0) {
            h = h.substring(0, num);
        }

        info.append("|");

        if (host instanceof Inet4Address) {
            info.append("1");
        } else if (host instanceof Inet6Address) {
            info.append("2");
        }
        info.append("|");
        info.append(h);
        info.append("|");
        info.append(port);
        info.append("|");

        return sendCommand(FTPCommand.EPRT, info.toString());
    }

    /***
     * A convenience method to send the FTP PASV command to the server,
     * receive the reply, and return the reply code.  Remember, it's up
     * to you to interpret the reply string containing the host/port
     * information.
     * <p>
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int pasv() throws IOException
    {
        return sendCommand(FTPCommand.PASV);
    }

     /***
     * A convenience method to send the FTP EPSV command to the server,
     * receive the reply, and return the reply code.  Remember, it's up
     * to you to interpret the reply string containing the host/port
     * information.
     * <p>
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     * @since 2.2
     ***/
    public int epsv() throws IOException
    {
        return sendCommand(FTPCommand.EPSV);
    }

    /**
     * A convenience method to send the FTP TYPE command for text files
     * to the server, receive the reply, and return the reply code.
     * @param fileType  The type of the file (one of the <code>FILE_TYPE</code>
     *              constants).
     * @param formatOrByteSize  The format of the file (one of the
     *              <code>_FORMAT</code> constants.  In the case of
     *              <code>LOCAL_FILE_TYPE</code>, the byte size.
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     */
    public int type(int fileType, int formatOrByteSize) throws IOException
    {
        StringBuilder arg = new StringBuilder();

        arg.append(__modes.charAt(fileType));
        arg.append(' ');
        if (fileType == LOCAL_FILE_TYPE) {
            arg.append(formatOrByteSize);
        } else {
            arg.append(__modes.charAt(formatOrByteSize));
        }

        return sendCommand(FTPCommand.TYPE, arg.toString());
    }


    /**
     * A convenience method to send the FTP TYPE command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @param fileType  The type of the file (one of the <code>FILE_TYPE</code>
     *              constants).
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     */
    public int type(int fileType) throws IOException
    {
        return sendCommand(FTPCommand.TYPE,
                           __modes.substring(fileType, fileType + 1));
    }

    /***
     * A convenience method to send the FTP STRU command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @param structure  The structure of the file (one of the
     *         <code>_STRUCTURE</code> constants).
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int stru(int structure) throws IOException
    {
        return sendCommand(FTPCommand.STRU,
                           __modes.substring(structure, structure + 1));
    }

    /***
     * A convenience method to send the FTP MODE command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @param mode  The transfer mode to use (one of the
     *         <code>TRANSFER_MODE</code> constants).
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int mode(int mode) throws IOException
    {
        return sendCommand(FTPCommand.MODE,
                           __modes.substring(mode, mode + 1));
    }

    /***
     * A convenience method to send the FTP RETR command to the server,
     * receive the reply, and return the reply code.  Remember, it is up
     * to you to manage the data connection.  If you don't need this low
     * level of access, use {@link org.apache.commons.net.ftp.FTPClient}
     * , which will handle all low level details for you.
     * <p>
     * @param pathname  The pathname of the file to retrieve.
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int retr(String pathname) throws IOException
    {
        return sendCommand(FTPCommand.RETR, pathname);
    }

    /***
     * A convenience method to send the FTP STOR command to the server,
     * receive the reply, and return the reply code.  Remember, it is up
     * to you to manage the data connection.  If you don't need this low
     * level of access, use {@link org.apache.commons.net.ftp.FTPClient}
     * , which will handle all low level details for you.
     * <p>
     * @param pathname  The pathname to use for the file when stored at
     *                  the remote end of the transfer.
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int stor(String pathname) throws IOException
    {
        return sendCommand(FTPCommand.STOR, pathname);
    }

    /***
     * A convenience method to send the FTP STOU command to the server,
     * receive the reply, and return the reply code.  Remember, it is up
     * to you to manage the data connection.  If you don't need this low
     * level of access, use {@link org.apache.commons.net.ftp.FTPClient}
     * , which will handle all low level details for you.
     * <p>
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int stou() throws IOException
    {
        return sendCommand(FTPCommand.STOU);
    }

    /***
     * A convenience method to send the FTP STOU command to the server,
     * receive the reply, and return the reply code.  Remember, it is up
     * to you to manage the data connection.  If you don't need this low
     * level of access, use {@link org.apache.commons.net.ftp.FTPClient}
     * , which will handle all low level details for you.
     * @param pathname  The base pathname to use for the file when stored at
     *                  the remote end of the transfer.  Some FTP servers
     *                  require this.
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     */
    public int stou(String pathname) throws IOException
    {
        return sendCommand(FTPCommand.STOU, pathname);
    }

    /***
     * A convenience method to send the FTP APPE command to the server,
     * receive the reply, and return the reply code.  Remember, it is up
     * to you to manage the data connection.  If you don't need this low
     * level of access, use {@link org.apache.commons.net.ftp.FTPClient}
     * , which will handle all low level details for you.
     * <p>
     * @param pathname  The pathname to use for the file when stored at
     *                  the remote end of the transfer.
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int appe(String pathname) throws IOException
    {
        return sendCommand(FTPCommand.APPE, pathname);
    }

    /***
     * A convenience method to send the FTP ALLO command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @param bytes The number of bytes to allocate.
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int allo(int bytes) throws IOException
    {
        return sendCommand(FTPCommand.ALLO, Integer.toString(bytes));
    }

    /**
     * A convenience method to send the FTP FEAT command to the server, receive the reply,
     * and return the reply code.
     * @return The reply code received by the server
     * @throws IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     * @since 2.2
     */
    public int feat() throws IOException
    {
        return sendCommand(FTPCommand.FEAT);
    }

    /***
     * A convenience method to send the FTP ALLO command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @param bytes The number of bytes to allocate.
     * @param recordSize  The size of a record.
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int allo(int bytes, int recordSize) throws IOException
    {
        return sendCommand(FTPCommand.ALLO, Integer.toString(bytes) + " R " +
                           Integer.toString(recordSize));
    }

    /***
     * A convenience method to send the FTP REST command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @param marker The marker at which to restart a transfer.
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int rest(String marker) throws IOException
    {
        return sendCommand(FTPCommand.REST, marker);
    }


    /**
     * @since 2.0
     **/
    public int mdtm(String file) throws IOException
    {
        return sendCommand(FTPCommand.MDTM, file);
    }


    /**
     * A convenience method to send the FTP MFMT command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @param pathname The pathname for which mtime is to be changed
     * @param timeval Timestamp in <code>YYYYMMDDhhmmss</code> format
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     * @since 2.2
     * @see <a href="http://tools.ietf.org/html/draft-somers-ftp-mfxx-04">http://tools.ietf.org/html/draft-somers-ftp-mfxx-04</a>
     **/
    public int mfmt(String pathname, String timeval) throws IOException
    {
        return sendCommand(FTPCommand.MFMT, timeval + " " + pathname);
    }


    /***
     * A convenience method to send the FTP RNFR command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @param pathname The pathname to rename from.
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int rnfr(String pathname) throws IOException
    {
        return sendCommand(FTPCommand.RNFR, pathname);
    }

    /***
     * A convenience method to send the FTP RNTO command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @param pathname The pathname to rename to
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int rnto(String pathname) throws IOException
    {
        return sendCommand(FTPCommand.RNTO, pathname);
    }

    /***
     * A convenience method to send the FTP DELE command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @param pathname The pathname to delete.
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int dele(String pathname) throws IOException
    {
        return sendCommand(FTPCommand.DELE, pathname);
    }

    /***
     * A convenience method to send the FTP RMD command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @param pathname The pathname of the directory to remove.
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int rmd(String pathname) throws IOException
    {
        return sendCommand(FTPCommand.RMD, pathname);
    }

    /***
     * A convenience method to send the FTP MKD command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @param pathname The pathname of the new directory to create.
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int mkd(String pathname) throws IOException
    {
        return sendCommand(FTPCommand.MKD, pathname);
    }

    /***
     * A convenience method to send the FTP PWD command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int pwd() throws IOException
    {
        return sendCommand(FTPCommand.PWD);
    }

    /***
     * A convenience method to send the FTP LIST command to the server,
     * receive the reply, and return the reply code.  Remember, it is up
     * to you to manage the data connection.  If you don't need this low
     * level of access, use {@link org.apache.commons.net.ftp.FTPClient}
     * , which will handle all low level details for you.
     * <p>
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int list() throws IOException
    {
        return sendCommand(FTPCommand.LIST);
    }

    /***
     * A convenience method to send the FTP LIST command to the server,
     * receive the reply, and return the reply code.  Remember, it is up
     * to you to manage the data connection.  If you don't need this low
     * level of access, use {@link org.apache.commons.net.ftp.FTPClient}
     * , which will handle all low level details for you.
     * <p>
     * @param pathname  The pathname to list,
     * may be {@code null} in which case the command is sent with no parameters
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int list(String pathname) throws IOException
    {
        return sendCommand(FTPCommand.LIST, pathname);
    }

    /**
     * A convenience method to send the FTP MLSD command to the server,
     * receive the reply, and return the reply code.  Remember, it is up
     * to you to manage the data connection.  If you don't need this low
     * level of access, use {@link org.apache.commons.net.ftp.FTPClient}
     * , which will handle all low level details for you.
     * <p>
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     * @since 3.0
     */
    public int mlsd() throws IOException
    {
        return sendCommand(FTPCommand.MLSD);
    }

    /**
     * A convenience method to send the FTP MLSD command to the server,
     * receive the reply, and return the reply code.  Remember, it is up
     * to you to manage the data connection.  If you don't need this low
     * level of access, use {@link org.apache.commons.net.ftp.FTPClient}
     * , which will handle all low level details for you.
     * <p>
     * @param path the path to report on
     * @return The reply code received from the server,
     * may be {@code null} in which case the command is sent with no parameters
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     * @since 3.0
     */
    public int mlsd(String path) throws IOException
    {
        return sendCommand(FTPCommand.MLSD, path);
    }

    /**
     * A convenience method to send the FTP MLST command to the server,
     * receive the reply, and return the reply code.  Remember, it is up
     * to you to manage the data connection.  If you don't need this low
     * level of access, use {@link org.apache.commons.net.ftp.FTPClient}
     * , which will handle all low level details for you.
     * <p>
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     * @since 3.0
     */
    public int mlst() throws IOException
    {
        return sendCommand(FTPCommand.MLST);
    }

    /**
     * A convenience method to send the FTP MLST command to the server,
     * receive the reply, and return the reply code.  Remember, it is up
     * to you to manage the data connection.  If you don't need this low
     * level of access, use {@link org.apache.commons.net.ftp.FTPClient}
     * , which will handle all low level details for you.
     * <p>
     * @param path the path to report on
     * @return The reply code received from the server,
     * may be {@code null} in which case the command is sent with no parameters
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     * @since 3.0
     */
    public int mlst(String path) throws IOException
    {
        return sendCommand(FTPCommand.MLST, path);
    }

    /***
     * A convenience method to send the FTP NLST command to the server,
     * receive the reply, and return the reply code.  Remember, it is up
     * to you to manage the data connection.  If you don't need this low
     * level of access, use {@link org.apache.commons.net.ftp.FTPClient}
     * , which will handle all low level details for you.
     * <p>
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int nlst() throws IOException
    {
        return sendCommand(FTPCommand.NLST);
    }

    /***
     * A convenience method to send the FTP NLST command to the server,
     * receive the reply, and return the reply code.  Remember, it is up
     * to you to manage the data connection.  If you don't need this low
     * level of access, use {@link org.apache.commons.net.ftp.FTPClient}
     * , which will handle all low level details for you.
     * <p>
     * @param pathname  The pathname to list,
     * may be {@code null} in which case the command is sent with no parameters
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int nlst(String pathname) throws IOException
    {
        return sendCommand(FTPCommand.NLST, pathname);
    }

    /***
     * A convenience method to send the FTP SITE command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @param parameters  The site parameters to send.
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int site(String parameters) throws IOException
    {
        return sendCommand(FTPCommand.SITE, parameters);
    }

    /***
     * A convenience method to send the FTP SYST command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int syst() throws IOException
    {
        return sendCommand(FTPCommand.SYST);
    }

    /***
     * A convenience method to send the FTP STAT command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int stat() throws IOException
    {
        return sendCommand(FTPCommand.STAT);
    }

    /***
     * A convenience method to send the FTP STAT command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @param pathname  A pathname to list.
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int stat(String pathname) throws IOException
    {
        return sendCommand(FTPCommand.STAT, pathname);
    }

    /***
     * A convenience method to send the FTP HELP command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int help() throws IOException
    {
        return sendCommand(FTPCommand.HELP);
    }

    /***
     * A convenience method to send the FTP HELP command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @param command  The command name on which to request help.
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int help(String command) throws IOException
    {
        return sendCommand(FTPCommand.HELP, command);
    }

    /***
     * A convenience method to send the FTP NOOP command to the server,
     * receive the reply, and return the reply code.
     * <p>
     * @return The reply code received from the server.
     * @exception FTPConnectionClosedException
     *      If the FTP server prematurely closes the connection as a result
     *      of the client being idle or some other reason causing the server
     *      to send FTP reply code 421.  This exception may be caught either
     *      as an IOException or independently as itself.
     * @exception IOException  If an I/O error occurs while either sending the
     *      command or receiving the server reply.
     ***/
    public int noop() throws IOException
    {
        return sendCommand(FTPCommand.NOOP);
    }

    /**
     * Return whether strict multiline parsing is enabled, as per RFC 959, section 4.2.
     * @return True if strict, false if lenient
     * @since 2.0
     */
    public boolean isStrictMultilineParsing() {
        return strictMultilineParsing;
    }

    /**
     * Set strict multiline parsing.
     * @param strictMultilineParsing
     * @since 2.0
     */
    public void setStrictMultilineParsing(boolean strictMultilineParsing) {
        this.strictMultilineParsing = strictMultilineParsing;
    }

    /**
     * Provide command support to super-class
     */
    @Override
    protected ProtocolCommandSupport getCommandSupport() {
        return _commandSupport_;
    }
}

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