    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
    018    package 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
    027    public 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    }