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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  
18  package org.apache.commons.net.telnet;
19  
20  /**
21   * The TelnetCommand class cannot be instantiated and only serves as a
22   * storehouse for telnet command constants.
23   * @see org.apache.commons.net.telnet.Telnet
24   * @see org.apache.commons.net.telnet.TelnetClient
25   */
26  
27  public final class TelnetCommand
28  {
29      /*** The maximum value a command code can have.  This value is 255. ***/
30      public static final int MAX_COMMAND_VALUE = 255;
31  
32      /*** Interpret As Command code.  Value is 255 according to RFC 854. ***/
33      public static final int IAC = 255;
34  
35      /*** Don't use option code.  Value is 254 according to RFC 854. ***/
36      public static final int DONT = 254;
37  
38      /*** Request to use option code.  Value is 253 according to RFC 854. ***/
39      public static final int DO = 253;
40  
41      /*** Refuse to use option code.  Value is 252 according to RFC 854. ***/
42      public static final int WONT = 252;
43  
44      /*** Agree to use option code.  Value is 251 according to RFC 854. ***/
45      public static final int WILL = 251;
46  
47      /*** Start subnegotiation code.  Value is 250 according to RFC 854. ***/
48      public static final int SB = 250;
49  
50      /*** Go Ahead code.  Value is 249 according to RFC 854. ***/
51      public static final int GA = 249;
52  
53      /*** Erase Line code.  Value is 248 according to RFC 854. ***/
54      public static final int EL = 248;
55  
56      /*** Erase Character code.  Value is 247 according to RFC 854. ***/
57      public static final int EC = 247;
58  
59      /*** Are You There code.  Value is 246 according to RFC 854. ***/
60      public static final int AYT = 246;
61  
62      /*** Abort Output code.  Value is 245 according to RFC 854. ***/
63      public static final int AO = 245;
64  
65      /*** Interrupt Process code.  Value is 244 according to RFC 854. ***/
66      public static final int IP = 244;
67  
68      /*** Break code.  Value is 243 according to RFC 854. ***/
69      public static final int BREAK = 243;
70  
71      /*** Data mark code.  Value is 242 according to RFC 854. ***/
72      public static final int DM = 242;
73  
74      /*** No Operation code.  Value is 241 according to RFC 854. ***/
75      public static final int NOP = 241;
76  
77      /*** End subnegotiation code.  Value is 240 according to RFC 854. ***/
78      public static final int SE = 240;
79  
80      /*** End of record code.  Value is 239. ***/
81      public static final int EOR = 239;
82  
83      /*** Abort code.  Value is 238. ***/
84      public static final int ABORT = 238;
85  
86      /*** Suspend process code.  Value is 237. ***/
87      public static final int SUSP = 237;
88  
89      /*** End of file code.  Value is 236. ***/
90      public static final int EOF = 236;
91  
92      /*** Synchronize code.  Value is 242. ***/
93      public static final int SYNCH = 242;
94  
95      /*** String representations of commands. ***/
96      private static final String __commandString[] = {
97                  "IAC", "DONT", "DO", "WONT", "WILL", "SB", "GA", "EL", "EC", "AYT",
98                  "AO", "IP", "BRK", "DMARK", "NOP", "SE", "EOR", "ABORT", "SUSP", "EOF"
99              };
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 }