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     * @author Daniel F. Savarese
024     * @see org.apache.commons.net.telnet.Telnet
025     * @see org.apache.commons.net.telnet.TelnetClient
026     */
027    
028    public final class TelnetCommand
029    {
030        /*** The maximum value a command code can have.  This value is 255. ***/
031        public static final int MAX_COMMAND_VALUE = 255;
032    
033        /*** Interpret As Command code.  Value is 255 according to RFC 854. ***/
034        public static final int IAC = 255;
035    
036        /*** Don't use option code.  Value is 254 according to RFC 854. ***/
037        public static final int DONT = 254;
038    
039        /*** Request to use option code.  Value is 253 according to RFC 854. ***/
040        public static final int DO = 253;
041    
042        /*** Refuse to use option code.  Value is 252 according to RFC 854. ***/
043        public static final int WONT = 252;
044    
045        /*** Agree to use option code.  Value is 251 according to RFC 854. ***/
046        public static final int WILL = 251;
047    
048        /*** Start subnegotiation code.  Value is 250 according to RFC 854. ***/
049        public static final int SB = 250;
050    
051        /*** Go Ahead code.  Value is 249 according to RFC 854. ***/
052        public static final int GA = 249;
053    
054        /*** Erase Line code.  Value is 248 according to RFC 854. ***/
055        public static final int EL = 248;
056    
057        /*** Erase Character code.  Value is 247 according to RFC 854. ***/
058        public static final int EC = 247;
059    
060        /*** Are You There code.  Value is 246 according to RFC 854. ***/
061        public static final int AYT = 246;
062    
063        /*** Abort Output code.  Value is 245 according to RFC 854. ***/
064        public static final int AO = 245;
065    
066        /*** Interrupt Process code.  Value is 244 according to RFC 854. ***/
067        public static final int IP = 244;
068    
069        /*** Break code.  Value is 243 according to RFC 854. ***/
070        public static final int BREAK = 243;
071    
072        /*** Data mark code.  Value is 242 according to RFC 854. ***/
073        public static final int DM = 242;
074    
075        /*** No Operation code.  Value is 241 according to RFC 854. ***/
076        public static final int NOP = 241;
077    
078        /*** End subnegotiation code.  Value is 240 according to RFC 854. ***/
079        public static final int SE = 240;
080    
081        /*** End of record code.  Value is 239. ***/
082        public static final int EOR = 239;
083    
084        /*** Abort code.  Value is 238. ***/
085        public static final int ABORT = 238;
086    
087        /*** Suspend process code.  Value is 237. ***/
088        public static final int SUSP = 237;
089    
090        /*** End of file code.  Value is 236. ***/
091        public static final int EOF = 236;
092    
093        /*** Synchronize code.  Value is 242. ***/
094        public static final int SYNCH = 242;
095    
096        /*** String representations of commands. ***/
097        private static final String __commandString[] = {
098                    "IAC", "DONT", "DO", "WONT", "WILL", "SB", "GA", "EL", "EC", "AYT",
099                    "AO", "IP", "BRK", "DMARK", "NOP", "SE", "EOR", "ABORT", "SUSP", "EOF"
100                };
101    
102        private static final int __FIRST_COMMAND = IAC;
103        private static final int __LAST_COMMAND = EOF;
104    
105        /***
106         * Returns the string representation of the telnet protocol command
107         * corresponding to the given command code.
108         * <p>
109         * @param code The command code of the telnet protocol command.
110         * @return The string representation of the telnet protocol command.
111         ***/
112        public static final String getCommand(int code)
113        {
114            return __commandString[__FIRST_COMMAND - code];
115        }
116    
117        /***
118         * Determines if a given command code is valid.  Returns true if valid,
119         * false if not.
120         * <p>
121         * @param code  The command code to test.
122         * @return True if the command code is valid, false if not.
123         **/
124        public static final boolean isValidCommand(int code)
125        {
126            return (code <= __FIRST_COMMAND && code >= __LAST_COMMAND);
127        }
128    
129        // Cannot be instantiated
130        private TelnetCommand()
131        { }
132    }