FTP.java

/*
 * 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.io.Reader;
import java.net.Inet4Address;
import java.net.Inet6Address;
import java.net.InetAddress;
import java.net.SocketException;
import java.net.SocketTimeoutException;
import java.nio.charset.StandardCharsets;
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;
import org.apache.commons.net.util.NetConstants;

/**
 * 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>
 * <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 periodically sending NOOP commands to the server.
 * </p>
 * <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>
 *
 * @see FTPClient
 * @see FTPConnectionClosedException
 * @see org.apache.commons.net.MalformedServerReplyException
 */

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 transferred 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 transferred should be treated as EBCDIC. Note however that there are several 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 transferred 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 transferred 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 transferred 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 transferred 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 transferred as FTP compressed data. All constants ending in <code>TRANSFER_MODE</code> are used to indicate
     * file transfer modes. Currently unused.
     */
    public static final int COMPRESSED_TRANSFER_MODE = 12;

    /**
     * A constant used to indicate a file is to be transferred as FTP (un)compressing data in the "deflate" compression format. All constants ending in
     * <code>TRANSFER_MODE</code> are used to indicate file transfer modes.
     *
     * See the Internet Draft <a href="https://datatracker.ietf.org/doc/html/draft-preston-ftpext-deflate-04">Deflate transmission mode for FTP</a>
     */
    public static final int DEFLATE_TRANSFER_MODE = 13;

//    /**
//     * A constant used to indicate a file is to be transferred as FTP (un)compressing data in the GZIP compression format. All constants ending in
//     * <code>TRANSFER_MODE</code> are used to indicate file transfer modes.
//     */
//    public static final int GZIP_TRANSFER_MODE = 14;

    // 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 = StandardCharsets.ISO_8859_1.name();

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

    private static final String MODES = "AEILNTCFRPSBCZ";
    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 the 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;

    /**
     * If this is true, then non-multiline replies must have the format: 3-digit code <space> <text> If false, then the 3-digit code does not have to be
     * followed by space See section 4.2 of RFC 959 for details.
     */
    private boolean strictReplyParsing = true;

    /**
     * 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() {
        setDefaultPort(DEFAULT_PORT);
        _replyLines = new ArrayList<>();
        _newReplyString = false;
        _replyString = null;
        _controlEncoding = DEFAULT_CONTROL_ENCODING;
        _commandSupport_ = new ProtocolCommandSupport(this);
    }

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

    /**
     * Send a noop and get the reply without reporting to the command listener. Intended for use with keep-alive.
     *
     * @throws IOException on error
     * @since 3.0
     */
    protected void __noop() throws IOException {
        final String msg = buildMessage(FTPCmd.NOOP.getCommand(), null);
        send(msg);
        __getReplyNoReport(); // This may time out
    }

    /**
     * Initiates control connections and gets initial reply. Initializes {@link #_controlInput_} and {@link #_controlOutput_}.
     */
    @Override
    protected void _connectAction_() throws IOException {
        _connectAction_(null);
    }

    /**
     * Initiates control connections and gets initial reply. Initializes {@link #_controlInput_} and {@link #_controlOutput_}.
     *
     * @param socketIsReader the reader to reuse (if non-null)
     * @throws IOException on error
     * @since 3.4
     */
    protected void _connectAction_(final Reader socketIsReader) throws IOException {
        super._connectAction_(); // sets up _input_ and _output_
        if (socketIsReader == null) {
            _controlInput_ = new CRLFLineReader(new InputStreamReader(_input_, getControlEncoding()));
        } else {
            _controlInput_ = new CRLFLineReader(socketIsReader);
        }
        _controlOutput_ = new BufferedWriter(new OutputStreamWriter(_output_, getControlEncoding()));
        if (connectTimeout > 0) { // NET-385
            final 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 (final SocketTimeoutException e) {
                final 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();
            }
        }
    }

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

    /**
     * A convenience method to send the FTP ACCT command to the server, receive the reply, and return the reply code.
     *
     * @param account The account name to access.
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int acct(final String account) throws IOException {
        return sendCommand(FTPCmd.ACCT, account);
    }

    /**
     * A convenience method to send the FTP ALLO command to the server, receive the reply, and return the reply code.
     *
     * @param bytes The number of bytes to allocate.
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int allo(final int bytes) throws IOException {
        return sendCommand(FTPCmd.ALLO, Integer.toString(bytes));
    }

    /**
     * A convenience method to send the FTP ALLO command to the server, receive the reply, and return the reply code.
     *
     * @param bytes      The number of bytes to allocate.
     * @param recordSize The size of a record.
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int allo(final int bytes, final int recordSize) throws IOException {
        return sendCommand(FTPCmd.ALLO, Integer.toString(bytes) + " R " + Integer.toString(recordSize));
    }

    /**
     * A convenience method to send the FTP ALLO command to the server, receive the reply, and return the reply code.
     *
     * @param bytes The number of bytes to allocate.
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int allo(final long bytes) throws IOException {
        return sendCommand(FTPCmd.ALLO, Long.toString(bytes));
    }

    /**
     * A convenience method to send the FTP ALLO command to the server, receive the reply, and return the reply code.
     *
     * @param bytes      The number of bytes to allocate.
     * @param recordSize The size of a record.
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int allo(final long bytes, final int recordSize) throws IOException {
        return sendCommand(FTPCmd.ALLO, Long.toString(bytes) + " R " + Integer.toString(recordSize));
    }

    /**
     * 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.
     *
     * @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.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int appe(final String pathname) throws IOException {
        return sendCommand(FTPCmd.APPE, pathname);
    }

    private String buildMessage(final String command, final 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();
    }

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

    private int checkMode(final int index) {
        if (index >= MODES.length()) {
            throw new IllegalArgumentException("Unknown mode");
        }
        return index;
    }

    /**
     * A convenience method to send the FTP CWD command to the server, receive the reply, and return the reply code.
     *
     * @param directory The new working directory.
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int cwd(final String directory) throws IOException {
        return sendCommand(FTPCmd.CWD, directory);
    }

    /**
     * A convenience method to send the FTP DELE command to the server, receive the reply, and return the reply code.
     *
     * @param pathname The pathname to delete.
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int dele(final String pathname) throws IOException {
        return sendCommand(FTPCmd.DELE, pathname);
    }

    /**
     * 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.
     *
     * @throws IOException If an error occurs while disconnecting.
     */
    @Override
    public void disconnect() throws IOException {
        super.disconnect();
        _controlInput_ = null;
        _controlOutput_ = null;
        _newReplyString = false;
        _replyString = null;
    }

    /**
     * A convenience method to send the FTP EPRT command to the server, receive the reply, and return the reply code.
     *
     * Examples:
     * <ul>
     * <li>EPRT |1|132.235.1.2|6275|</li>
     * <li>EPRT |2|1080::8:800:200C:417A|5282|</li>
     * </ul>
     *
     * @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.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     * @since 2.2
     */
    public int eprt(final InetAddress host, final int port) throws IOException {
        final int num;
        final 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(FTPCmd.EPRT, info.toString());
    }

    /**
     * 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.
     *
     * @return The reply code received from the server.
     * @throws 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.
     * @throws 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(FTPCmd.EPSV);
    }

    /**
     * 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(FTPCmd.FEAT);
    }

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

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

    /**
     * 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.
     *
     * @return The integer value of the reply code of the fetched FTP reply.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while receiving the server reply.
     */
    public int getReply() throws IOException {
        return getReply(true);
    }

    private int getReply(final boolean reportReply) throws IOException {
        final 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;
        try {
            code = line.substring(0, REPLY_CODE_LEN);
            _replyCode = Integer.parseInt(code);
        } catch (final NumberFormatException e) {
            throw new MalformedServerReplyException("Could not parse response code.\nServer Reply: " + line);
        }

        _replyLines.add(line);

        // Check the server reply type
        if (length > REPLY_CODE_LEN) {
            final char sep = line.charAt(REPLY_CODE_LEN);
            // Get extra lines if message continues.
            if (sep == '-') {
                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));

            } else if (isStrictReplyParsing()) {
                if (length == REPLY_CODE_LEN + 1) { // expecting some text
                    throw new MalformedServerReplyException("Truncated server reply: '" + line + "'");
                }
                if (sep != ' ') {
                    throw new MalformedServerReplyException("Invalid server reply: '" + line + "'");
                }
            }
        } else if (isStrictReplyParsing()) {
            throw new MalformedServerReplyException("Truncated server reply: '" + line + "'");
        }

        if (reportReply) {
            fireReplyReceived(_replyCode, getReplyString());
        }

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

    /**
     * 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.
     *
     * @return The integer value of the reply code of the last FTP reply.
     */
    public int getReplyCode() {
        return _replyCode;
    }

    /**
     * Returns the entire text of the last FTP server response exactly as it was received, including all end of line markers in NETASCII format.
     *
     * @return The entire text from the last FTP response as a String.
     */
    public String getReplyString() {
        if (!_newReplyString) {
            return _replyString;
        }
        final StringBuilder buffer = new StringBuilder(256);
        for (final String line : _replyLines) {
            buffer.append(line);
            buffer.append(SocketClient.NETASCII_EOL);
        }
        _newReplyString = false;
        return _replyString = buffer.toString();
    }

    /**
     * Returns the nth line of text from the last FTP server response as a string. The end of line markers of each are stripped from the line.
     *
     * @param index The index of the line to return, 0-based.
     *
     * @return The lines of text from the last FTP response as an array.
     */
    String getReplyString(final int index) {
        return _replyLines.get(index);
    }

    /**
     * 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.
     *
     * @return The lines of text from the last FTP response as an array.
     */
    public String[] getReplyStrings() {
        return _replyLines.toArray(NetConstants.EMPTY_STRING_ARRAY);
    }

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

    /**
     * A convenience method to send the FTP HELP command to the server, receive the reply, and return the reply code.
     *
     * @param command The command name on which to request help.
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int help(final String command) throws IOException {
        return sendCommand(FTPCmd.HELP, command);
    }

    /**
     * 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;
    }

    /**
     * Return whether strict non-multiline parsing is enabled, as per RFC 959, section 4.2.
     * <p>
     * The default is true, which requires the 3-digit code be followed by space and some text. <br>
     * If false, only the 3-digit code is required (as was the case for versions up to 3.5) <br>
     *
     * @return True if strict (default), false if additional checks are not made
     * @since 3.6
     */
    public boolean isStrictReplyParsing() {
        return strictReplyParsing;
    }

    // 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(final String line) {
        return !(line.length() > REPLY_CODE_LEN && line.charAt(REPLY_CODE_LEN) != '-' && Character.isDigit(line.charAt(0)));
    }

    /**
     * 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.
     *
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int list() throws IOException {
        return sendCommand(FTPCmd.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.
     *
     * @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.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int list(final String pathname) throws IOException {
        return sendCommand(FTPCmd.LIST, pathname);
    }

    /**
     * Sends the MDTM command for the given file.
     *
     * @param file name of file
     * @return the status
     * @throws IOException on error
     * @since 2.0
     **/
    public int mdtm(final String file) throws IOException {
        return sendCommand(FTPCmd.MDTM, file);
    }

    /**
     * A convenience method to send the FTP MFMT command to the server, receive the reply, and return the reply code.
     *
     * @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.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     * @since 2.2
     * @see <a href="https://tools.ietf.org/html/draft-somers-ftp-mfxx-04">https://tools.ietf.org/html/draft-somers-ftp-mfxx-04</a>
     **/
    public int mfmt(final String pathname, final String timeval) throws IOException {
        return sendCommand(FTPCmd.MFMT, timeval + " " + pathname);
    }

    /**
     * A convenience method to send the FTP MKD command to the server, receive the reply, and return the reply code.
     *
     * @param pathname The pathname of the new directory to create.
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int mkd(final String pathname) throws IOException {
        return sendCommand(FTPCmd.MKD, 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.
     *
     * @return The reply code received from the server.
     * @throws 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.
     * @throws 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(FTPCmd.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.
     *
     * @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
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     * @since 3.0
     */
    public int mlsd(final String path) throws IOException {
        return sendCommand(FTPCmd.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.
     *
     * @return The reply code received from the server.
     * @throws 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.
     * @throws 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(FTPCmd.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.
     *
     * @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
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     * @since 3.0
     */
    public int mlst(final String path) throws IOException {
        return sendCommand(FTPCmd.MLST, path);
    }

    /**
     * A convenience method to send the FTP MODE command to the server, receive the reply, and return the reply code.
     *
     * @param mode The transfer mode to use (one of the <code>TRANSFER_MODE</code> constants).
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int mode(final int mode) throws IOException {

        return sendCommand(FTPCmd.MODE, modeStringAt(mode));
    }

    private char modeCharAt(final int index) {
        return MODES.charAt(checkMode(index));
    }

    private String modeStringAt(final int index) {
        checkMode(index);
        return MODES.substring(index, index + 1);
    }

    /**
     * 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.
     *
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int nlst() throws IOException {
        return sendCommand(FTPCmd.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.
     *
     * @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.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int nlst(final String pathname) throws IOException {
        return sendCommand(FTPCmd.NLST, pathname);
    }

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

    /**
     * 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 user being logged into.
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int pass(final String password) throws IOException {
        return sendCommand(FTPCmd.PASS, password);
    }

    /**
     * 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.
     *
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int pasv() throws IOException {
        return sendCommand(FTPCmd.PASV);
    }

    /**
     * A convenience method to send the FTP PORT command to the server, receive the reply, and return the reply code.
     *
     * @param host The host owning the port.
     * @param port The new port.
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int port(final InetAddress host, final int port) throws IOException {
        int num;
        final 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(FTPCmd.PORT, info.toString());
    }

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

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

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

    /**
     * A convenience method to send the FTP REST command to the server, receive the reply, and return the reply code.
     *
     * @param marker The marker at which to restart a transfer.
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int rest(final String marker) throws IOException {
        return sendCommand(FTPCmd.REST, marker);
    }

    /**
     * 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.
     *
     * @param pathname The pathname of the file to retrieve.
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int retr(final String pathname) throws IOException {
        return sendCommand(FTPCmd.RETR, pathname);
    }

    /**
     * A convenience method to send the FTP RMD command to the server, receive the reply, and return the reply code.
     *
     * @param pathname The pathname of the directory to remove.
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int rmd(final String pathname) throws IOException {
        return sendCommand(FTPCmd.RMD, pathname);
    }

    /**
     * A convenience method to send the FTP RNFR command to the server, receive the reply, and return the reply code.
     *
     * @param pathname The pathname to rename from.
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int rnfr(final String pathname) throws IOException {
        return sendCommand(FTPCmd.RNFR, pathname);
    }

    /**
     * A convenience method to send the FTP RNTO command to the server, receive the reply, and return the reply code.
     *
     * @param pathname The pathname to rename to
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int rnto(final String pathname) throws IOException {
        return sendCommand(FTPCmd.RNTO, pathname);
    }

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

    /**
     * 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 }.
     *
     * @param command The FTPCmd enum 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.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     * @since 3.3
     */
    public int sendCommand(final FTPCmd command) throws IOException {
        return sendCommand(command, 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 }.
     *
     * @param command The FTPCmd enum 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.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     * @since 3.3
     */
    public int sendCommand(final FTPCmd command, final String args) throws IOException {
        return sendCommand(command.getCommand(), 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 }.
     *
     * @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.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int sendCommand(final int command) throws IOException {
        return sendCommand(command, 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 }.
     *
     * @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.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     * @deprecated (3.3) Use {@link #sendCommand(FTPCmd, String)} instead
     */
    @Deprecated
    public int sendCommand(final int command, final 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 }.
     *
     * @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.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int sendCommand(final String command) throws IOException {
        return sendCommand(command, 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 }.
     *
     * @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.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int sendCommand(final String command, final 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);
        return getReply();
    }

    /**
     * Saves the character encoding to be used by the FTP control connection. Some FTP servers require that commands be issued in a non-ASCII encoding like
     * UTF-8 so that file names with multi-byte character representations (e.g, Big 8) can be specified.
     * <p>
     * Please note that this has to be set before the connection is established.
     *
     * @param encoding The new character encoding for the control connection.
     */
    public void setControlEncoding(final String encoding) {
        _controlEncoding = encoding;
    }

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

    /**
     * Sets strict non-multiline parsing.
     * <p>
     * If true, it requires the 3-digit code be followed by space and some text. <br>
     * If false, only the 3-digit code is required (as was the case for versions up to 3.5)
     * <p>
     * <b>This should not be required by a well-behaved FTP server</b> <br>
     *
     * @param strictReplyParsing the setting
     * @since 3.6
     */
    public void setStrictReplyParsing(final boolean strictReplyParsing) {
        this.strictReplyParsing = strictReplyParsing;
    }

    /**
     * A convenience method to send the FTP SITE command to the server, receive the reply, and return the reply code.
     *
     * @param parameters The site parameters to send.
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int site(final String parameters) throws IOException {
        return sendCommand(FTPCmd.SITE, parameters);
    }

    /**
     * A convenience method to send the FTP SIZE command to the server, receive the reply, and return the reply code.
     *
     * @param parameters The site parameters to send.
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     * @since 3.7
     */
    public int size(final String parameters) throws IOException {
        return sendCommand(FTPCmd.SIZE, parameters);
    }

    /**
     * A convenience method to send the FTP SMNT command to the server, receive the reply, and return the reply code.
     *
     * @param dir The directory name.
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int smnt(final String dir) throws IOException {
        return sendCommand(FTPCmd.SMNT, dir);
    }

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

    /**
     * A convenience method to send the FTP STAT command to the server, receive the reply, and return the reply code.
     *
     * @param pathname A pathname to list.
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int stat(final String pathname) throws IOException {
        return sendCommand(FTPCmd.STAT, 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.
     *
     * @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.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int stor(final String pathname) throws IOException {
        return sendCommand(FTPCmd.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.
     *
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int stou() throws IOException {
        return sendCommand(FTPCmd.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.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int stou(final String pathname) throws IOException {
        return sendCommand(FTPCmd.STOU, pathname);
    }

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

    /**
     * A convenience method to send the FTP STRU command to the server, receive the reply, and return the reply code.
     *
     * @param structure The structure of the file (one of the <code>_STRUCTURE</code> constants).
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int stru(final int structure) throws IOException {
        return sendCommand(FTPCmd.STRU, modeStringAt(structure));
    }

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

    /**
     * A convenience method to send the FTP TYPE command 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).
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int type(final int fileType) throws IOException {
        return sendCommand(FTPCmd.TYPE, modeStringAt(fileType));
    }

    /**
     * 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.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int type(final int fileType, final int formatOrByteSize) throws IOException {
        final StringBuilder arg = new StringBuilder();
        arg.append(modeCharAt(fileType));
        arg.append(' ');
        if (fileType == LOCAL_FILE_TYPE) {
            arg.append(formatOrByteSize);
        } else {
            arg.append(modeCharAt(formatOrByteSize));
        }

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

    /**
     * A convenience method to send the FTP USER command to the server, receive the reply, and return the reply code.
     *
     * @param user The user to login under.
     * @return The reply code received from the server.
     * @throws 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.
     * @throws IOException                  If an I/O error occurs while either sending the command or receiving the server reply.
     */
    public int user(final String user) throws IOException {
        return sendCommand(FTPCmd.USER, user);
    }
}