001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018package org.apache.commons.net.telnet;
019
020/**
021 * The TelnetCommand class cannot be instantiated and only serves as a
022 * storehouse for telnet command constants.
023 * @see org.apache.commons.net.telnet.Telnet
024 * @see org.apache.commons.net.telnet.TelnetClient
025 */
026
027public final class TelnetCommand
028{
029    /*** The maximum value a command code can have.  This value is 255. ***/
030    public static final int MAX_COMMAND_VALUE = 255;
031
032    /*** Interpret As Command code.  Value is 255 according to RFC 854. ***/
033    public static final int IAC = 255;
034
035    /*** Don't use option code.  Value is 254 according to RFC 854. ***/
036    public static final int DONT = 254;
037
038    /*** Request to use option code.  Value is 253 according to RFC 854. ***/
039    public static final int DO = 253;
040
041    /*** Refuse to use option code.  Value is 252 according to RFC 854. ***/
042    public static final int WONT = 252;
043
044    /*** Agree to use option code.  Value is 251 according to RFC 854. ***/
045    public static final int WILL = 251;
046
047    /*** Start subnegotiation code.  Value is 250 according to RFC 854. ***/
048    public static final int SB = 250;
049
050    /*** Go Ahead code.  Value is 249 according to RFC 854. ***/
051    public static final int GA = 249;
052
053    /*** Erase Line code.  Value is 248 according to RFC 854. ***/
054    public static final int EL = 248;
055
056    /*** Erase Character code.  Value is 247 according to RFC 854. ***/
057    public static final int EC = 247;
058
059    /*** Are You There code.  Value is 246 according to RFC 854. ***/
060    public static final int AYT = 246;
061
062    /*** Abort Output code.  Value is 245 according to RFC 854. ***/
063    public static final int AO = 245;
064
065    /*** Interrupt Process code.  Value is 244 according to RFC 854. ***/
066    public static final int IP = 244;
067
068    /*** Break code.  Value is 243 according to RFC 854. ***/
069    public static final int BREAK = 243;
070
071    /*** Data mark code.  Value is 242 according to RFC 854. ***/
072    public static final int DM = 242;
073
074    /*** No Operation code.  Value is 241 according to RFC 854. ***/
075    public static final int NOP = 241;
076
077    /*** End subnegotiation code.  Value is 240 according to RFC 854. ***/
078    public static final int SE = 240;
079
080    /*** End of record code.  Value is 239. ***/
081    public static final int EOR = 239;
082
083    /*** Abort code.  Value is 238. ***/
084    public static final int ABORT = 238;
085
086    /*** Suspend process code.  Value is 237. ***/
087    public static final int SUSP = 237;
088
089    /*** End of file code.  Value is 236. ***/
090    public static final int EOF = 236;
091
092    /*** Synchronize code.  Value is 242. ***/
093    public static final int SYNCH = 242;
094
095    /*** String representations of commands. ***/
096    private static final String __commandString[] = {
097                "IAC", "DONT", "DO", "WONT", "WILL", "SB", "GA", "EL", "EC", "AYT",
098                "AO", "IP", "BRK", "DMARK", "NOP", "SE", "EOR", "ABORT", "SUSP", "EOF"
099            };
100
101    private static final int __FIRST_COMMAND = IAC;
102    private static final int __LAST_COMMAND = EOF;
103
104    /***
105     * Returns the string representation of the telnet protocol command
106     * corresponding to the given command code.
107     * <p>
108     * @param code The command code of the telnet protocol command.
109     * @return The string representation of the telnet protocol command.
110     ***/
111    public static final String getCommand(int code)
112    {
113        return __commandString[__FIRST_COMMAND - code];
114    }
115
116    /***
117     * Determines if a given command code is valid.  Returns true if valid,
118     * false if not.
119     * <p>
120     * @param code  The command code to test.
121     * @return True if the command code is valid, false if not.
122     **/
123    public static final boolean isValidCommand(int code)
124    {
125        return (code <= __FIRST_COMMAND && code >= __LAST_COMMAND);
126    }
127
128    // Cannot be instantiated
129    private TelnetCommand()
130    { }
131}