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 * https://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 storehouse for Telnet command constants.
22 *
23 * @see org.apache.commons.net.telnet.Telnet
24 * @see org.apache.commons.net.telnet.TelnetClient
25 */
26
27 public final class TelnetCommand {
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 = { "IAC", "DONT", "DO", "WONT", "WILL", "SB", "GA", "EL", "EC", "AYT", "AO", "IP", "BRK", "DMARK", "NOP", "SE",
96 "EOR", "ABORT", "SUSP", "EOF" };
97
98 private static final int FIRST_COMMAND = IAC;
99 private static final int LAST_COMMAND = EOF;
100
101 /**
102 * Gets the string representation of the Telnet protocol command corresponding to the given command code.
103 *
104 * @param code The command code of the Telnet protocol command.
105 * @return The string representation of the Telnet protocol command.
106 */
107 public static String getCommand(final int code) {
108 return commandString[FIRST_COMMAND - code];
109 }
110
111 /**
112 * Tests if a given command code is valid. Returns true if valid, false if not.
113 *
114 * @param code The command code to test.
115 * @return True if the command code is valid, false if not.
116 **/
117 public static boolean isValidCommand(final int code) {
118 return code <= FIRST_COMMAND && code >= LAST_COMMAND;
119 }
120
121 /** Cannot be instantiated. */
122 private TelnetCommand() {
123 }
124 }