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 * @author Daniel F. Savarese
024 * @see org.apache.commons.net.telnet.Telnet
025 * @see org.apache.commons.net.telnet.TelnetClient
026 */
027
028public 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}