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.tftp;
19
20 import java.net.DatagramPacket;
21 import java.net.InetAddress;
22
23 /**
24 * TFTPPacket is an abstract class encapsulating the functionality common to the 5 types of TFTP packets. It also provides a static factory method that will
25 * create the correct TFTP packet instance from a datagram. This relieves the programmer from having to figure out what kind of TFTP packet is contained in a
26 * datagram and create it himself.
27 * <p>
28 * Details regarding the TFTP protocol and the format of TFTP packets can be found in RFC 783. But the point of these classes is to keep you from having to
29 * worry about the internals. Additionally, only very few people should have to care about any of the TFTPPacket classes or derived classes. Almost all users
30 * should only be concerned with the {@link org.apache.commons.net.tftp.TFTPClient} class {@link org.apache.commons.net.tftp.TFTPClient#receiveFile
31 * receiveFile()} and {@link org.apache.commons.net.tftp.TFTPClient#sendFile sendFile()} methods.
32 *
33 *
34 * @see TFTPPacketException
35 * @see TFTP
36 */
37
38 public abstract class TFTPPacket {
39 /**
40 * The minimum size of a packet. This is 4 bytes. It is enough to store the opcode and blocknumber or other required data depending on the packet type.
41 */
42 static final int MIN_PACKET_SIZE = 4;
43
44 /**
45 * This is the actual TFTP spec identifier and is equal to 1. Identifier returned by {@link #getType getType()} indicating a read request packet.
46 */
47 public static final int READ_REQUEST = 1;
48
49 /**
50 * This is the actual TFTP spec identifier and is equal to 2. Identifier returned by {@link #getType getType()} indicating a write request packet.
51 */
52 public static final int WRITE_REQUEST = 2;
53
54 /**
55 * This is the actual TFTP spec identifier and is equal to 3. Identifier returned by {@link #getType getType()} indicating a data packet.
56 */
57 public static final int DATA = 3;
58
59 /**
60 * This is the actual TFTP spec identifier and is equal to 4. Identifier returned by {@link #getType getType()} indicating an acknowledgement packet.
61 */
62 public static final int ACKNOWLEDGEMENT = 4;
63
64 /**
65 * This is the actual TFTP spec identifier and is equal to 5. Identifier returned by {@link #getType getType()} indicating an error packet.
66 */
67 public static final int ERROR = 5;
68
69 /**
70 * The TFTP data packet maximum segment size in bytes. This is 512 and is useful for those familiar with the TFTP protocol who want to use the
71 * {@link org.apache.commons.net.tftp.TFTP} class methods to implement their own TFTP servers or clients.
72 */
73 public static final int SEGMENT_SIZE = 512;
74
75 /**
76 * When you receive a datagram that you expect to be a TFTP packet, you use this factory method to create the proper TFTPPacket object encapsulating the
77 * data contained in that datagram. This method is the only way you can instantiate a TFTPPacket derived class from a datagram.
78 *
79 * @param datagram The datagram containing a TFTP packet.
80 * @return The TFTPPacket object corresponding to the datagram.
81 * @throws TFTPPacketException If the datagram does not contain a valid TFTP packet.
82 */
83 public static final TFTPPacket newTFTPPacket(final DatagramPacket datagram) throws TFTPPacketException {
84 final byte[] data;
85 TFTPPacket packet;
86
87 if (datagram.getLength() < MIN_PACKET_SIZE) {
88 throw new TFTPPacketException("Bad packet. Datagram data length is too short.");
89 }
90
91 data = datagram.getData();
92
93 switch (data[1]) {
94 case READ_REQUEST:
95 packet = new TFTPReadRequestPacket(datagram);
96 break;
97 case WRITE_REQUEST:
98 packet = new TFTPWriteRequestPacket(datagram);
99 break;
100 case DATA:
101 packet = new TFTPDataPacket(datagram);
102 break;
103 case ACKNOWLEDGEMENT:
104 packet = new TFTPAckPacket(datagram);
105 break;
106 case ERROR:
107 packet = new TFTPErrorPacket(datagram);
108 break;
109 default:
110 throw new TFTPPacketException("Bad packet. Invalid TFTP operator code.");
111 }
112
113 return packet;
114 }
115
116 /** The type of packet. */
117 int type;
118
119 /** The port the packet came from or is going to. */
120 int port;
121
122 /** The host the packet is going to be sent or where it came from. */
123 InetAddress address;
124
125 /**
126 * This constructor is not visible outside the package. It is used by subclasses within the package to initialize base data.
127 *
128 * @param type The type of the packet.
129 * @param address The host the packet came from or is going to be sent.
130 * @param port The port the packet came from or is going to be sent.
131 **/
132 TFTPPacket(final int type, final InetAddress address, final int port) {
133 this.type = type;
134 this.address = address;
135 this.port = port;
136 }
137
138 /**
139 * Returns the address of the host where the packet is going to be sent or where it came from.
140 *
141 * @return The type of the packet.
142 */
143 public final InetAddress getAddress() {
144 return address;
145 }
146
147 /**
148 * Returns the port where the packet is going to be sent or where it came from.
149 *
150 * @return The port where the packet came from or where it is going.
151 */
152 public final int getPort() {
153 return port;
154 }
155
156 /**
157 * Returns the type of the packet.
158 *
159 * @return The type of the packet.
160 */
161 public final int getType() {
162 return type;
163 }
164
165 /**
166 * Creates a UDP datagram containing all the TFTP packet data in the proper format. This is an abstract method, exposed to the programmer in case he wants
167 * to implement his own TFTP client instead of using the {@link org.apache.commons.net.tftp.TFTPClient} class. Under normal circumstances, you should not
168 * have a need to call this method.
169 *
170 * @return A UDP datagram containing the TFTP packet.
171 */
172 public abstract DatagramPacket newDatagram();
173
174 /**
175 * This is an abstract method only available within the package for implementing efficient datagram transport by eliminating buffering. It takes a datagram
176 * as an argument, and a byte buffer in which to store the raw datagram data. Inside the method, the data should be set as the datagram's data and the
177 * datagram returned.
178 *
179 * @param datagram The datagram to create.
180 * @param data The buffer to store the packet and to use in the datagram.
181 * @return The datagram argument.
182 */
183 abstract DatagramPacket newDatagram(DatagramPacket datagram, byte[] data);
184
185 /**
186 * Sets the host address where the packet is going to be sent.
187 *
188 * @param address the address to set
189 */
190 public final void setAddress(final InetAddress address) {
191 this.address = address;
192 }
193
194 /**
195 * Sets the port where the packet is going to be sent.
196 *
197 * @param port the port to set
198 */
199 public final void setPort(final int port) {
200 this.port = port;
201 }
202
203 /**
204 * For debugging
205 *
206 * @since 3.6
207 */
208 @Override
209 public String toString() {
210 return address + " " + port + " " + type;
211 }
212 }