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    1   /*
    2    * Copyright 2001-2005 The Apache Software Foundation
    3    *
    4    * Licensed under the Apache License, Version 2.0 (the "License");
    5    * you may not use this file except in compliance with the License.
    6    * You may obtain a copy of the License at
    7    *
    8    *     http://www.apache.org/licenses/LICENSE-2.0
    9    *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS,
    12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13   * See the License for the specific language governing permissions and
    14   * limitations under the License.
    15   */
    16  package org.apache.commons.net.telnet;
    17
    18  /***
    19   * The TelnetCommand class cannot be instantiated and only serves as a
    20   * storehouse for telnet command constants.
    21   * @author Daniel F. Savarese
    22   * @see org.apache.commons.net.telnet.Telnet
    23   * @see org.apache.commons.net.telnet.TelnetClient
    24   */
    25
    26  public final class TelnetCommand
    27  {
    28      /**** The maximum value a command code can have.  This value is 255. ***/
    29      public static final int MAX_COMMAND_VALUE = 255;
    30
    31      /**** Interpret As Command code.  Value is 255 according to RFC 854. ***/
    32      public static final int IAC = 255;
    33
    34      /**** Don't use option code.  Value is 254 according to RFC 854. ***/
    35      public static final int DONT = 254;
    36
    37      /**** Request to use option code.  Value is 253 according to RFC 854. ***/
    38      public static final int DO = 253;
    39
    40      /**** Refuse to use option code.  Value is 252 according to RFC 854. ***/
    41      public static final int WONT = 252;
    42
    43      /**** Agree to use option code.  Value is 251 according to RFC 854. ***/
    44      public static final int WILL = 251;
    45
    46      /**** Start subnegotiation code.  Value is 250 according to RFC 854. ***/
    47      public static final int SB = 250;
    48
    49      /**** Go Ahead code.  Value is 249 according to RFC 854. ***/
    50      public static final int GA = 249;
    51
    52      /**** Erase Line code.  Value is 248 according to RFC 854. ***/
    53      public static final int EL = 248;
    54
    55      /**** Erase Character code.  Value is 247 according to RFC 854. ***/
    56      public static final int EC = 247;
    57
    58      /**** Are You There code.  Value is 246 according to RFC 854. ***/
    59      public static final int AYT = 246;
    60
    61      /**** Abort Output code.  Value is 245 according to RFC 854. ***/
    62      public static final int AO = 245;
    63
    64      /**** Interrupt Process code.  Value is 244 according to RFC 854. ***/
    65      public static final int IP = 244;
    66
    67      /**** Break code.  Value is 243 according to RFC 854. ***/
    68      public static final int BREAK = 243;
    69
    70      /**** Data mark code.  Value is 242 according to RFC 854. ***/
    71      public static final int DM = 242;
    72
    73      /**** No Operation code.  Value is 241 according to RFC 854. ***/
    74      public static final int NOP = 241;
    75
    76      /**** End subnegotiation code.  Value is 240 according to RFC 854. ***/
    77      public static final int SE = 240;
    78
    79      /**** End of record code.  Value is 239. ***/
    80      public static final int EOR = 239;
    81
    82      /**** Abort code.  Value is 238. ***/
    83      public static final int ABORT = 238;
    84
    85      /**** Suspend process code.  Value is 237. ***/
    86      public static final int SUSP = 237;
    87
    88      /**** End of file code.  Value is 236. ***/
    89      public static final int EOF = 236;
    90
    91      /**** Synchronize code.  Value is 242. ***/
    92      public static final int SYNCH = 242;
    93
    94      /**** String representations of commands. ***/
    95      private static final String __commandString[] = {
    96                  "IAC", "DONT", "DO", "WONT", "WILL", "SB", "GA", "EL", "EC", "AYT",
    97                  "AO", "IP", "BRK", "DMARK", "NOP", "SE", "EOR", "ABORT", "SUSP", "EOF"
    98              };
    99
    100     private static final int __FIRST_COMMAND = IAC;
    101     private static final int __LAST_COMMAND = EOF;
    102
    103     /****
    104      * Returns the string representation of the telnet protocol command
    105      * corresponding to the given command code.
    106      * <p>
    107      * @param code The command code of the telnet protocol command.
    108      * @return The string representation of the telnet protocol command.
    109      ***/
    110     public static final String getCommand(int code)
    111     {
    112         return __commandString[__FIRST_COMMAND - code];
    113     }
    114
    115     /****
    116      * Determines if a given command code is valid.  Returns true if valid,
    117      * false if not.
    118      * <p>
    119      * @param code  The command code to test.
    120      * @return True if the command code is valid, false if not.
    121      **/
    122     public static final boolean isValidCommand(int code)
    123     {
    124         return (code <= __FIRST_COMMAND && code >= __LAST_COMMAND);
    125     }
    126
    127     // Cannot be instantiated
    128     private TelnetCommand()
    129     { }
    130 }