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| org.apache.commons.net.tftp.TFTPPacket |
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| 1 | /* |
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| 2 | * Copyright 2001-2005 The Apache Software Foundation |
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| 3 | * |
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| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
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| 5 | * you may not use this file except in compliance with the License. |
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| 6 | * You may obtain a copy of the License at |
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| 7 | * |
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| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
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| 9 | * |
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| 10 | * Unless required by applicable law or agreed to in writing, software |
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| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
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| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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| 13 | * See the License for the specific language governing permissions and |
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| 14 | * limitations under the License. |
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| 15 | */ |
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| 16 | package org.apache.commons.net.tftp; |
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| 17 | ||
| 18 | import java.net.DatagramPacket; |
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| 19 | import java.net.InetAddress; |
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| 20 | ||
| 21 | /*** |
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| 22 | * TFTPPacket is an abstract class encapsulating the functionality common |
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| 23 | * to the 5 types of TFTP packets. It also provides a static factory |
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| 24 | * method that will create the correct TFTP packet instance from a |
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| 25 | * datagram. This relieves the programmer from having to figure out what |
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| 26 | * kind of TFTP packet is contained in a datagram and create it himself. |
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| 27 | * <p> |
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| 28 | * Details regarding the TFTP protocol and the format of TFTP packets can |
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| 29 | * be found in RFC 783. But the point of these classes is to keep you |
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| 30 | * from having to worry about the internals. Additionally, only very |
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| 31 | * few people should have to care about any of the TFTPPacket classes |
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| 32 | * or derived classes. Almost all users should only be concerned with the |
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| 33 | * {@link org.apache.commons.net.tftp.TFTPClient} class |
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| 34 | * {@link org.apache.commons.net.tftp.TFTPClient#receiveFile receiveFile()} |
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| 35 | * and |
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| 36 | * {@link org.apache.commons.net.tftp.TFTPClient#sendFile sendFile()} |
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| 37 | * methods. |
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| 38 | * <p> |
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| 39 | * <p> |
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| 40 | * @author Daniel F. Savarese |
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| 41 | * @see TFTPPacketException |
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| 42 | * @see TFTP |
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| 43 | ***/ |
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| 44 | ||
| 45 | public abstract class TFTPPacket |
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| 46 | { |
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| 47 | /*** |
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| 48 | * The minimum size of a packet. This is 4 bytes. It is enough |
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| 49 | * to store the opcode and blocknumber or other required data |
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| 50 | * depending on the packet type. |
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| 51 | ***/ |
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| 52 | static final int MIN_PACKET_SIZE = 4; |
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| 53 | ||
| 54 | /*** |
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| 55 | * This is the actual TFTP spec |
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| 56 | * identifier and is equal to 1. |
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| 57 | * Identifier returned by {@link #getType getType()} |
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| 58 | * indicating a read request packet. |
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| 59 | ***/ |
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| 60 | public static final int READ_REQUEST = 1; |
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| 61 | ||
| 62 | /*** |
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| 63 | * This is the actual TFTP spec |
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| 64 | * identifier and is equal to 2. |
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| 65 | * Identifier returned by {@link #getType getType()} |
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| 66 | * indicating a write request packet. |
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| 67 | ***/ |
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| 68 | public static final int WRITE_REQUEST = 2; |
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| 69 | ||
| 70 | /*** |
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| 71 | * This is the actual TFTP spec |
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| 72 | * identifier and is equal to 3. |
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| 73 | * Identifier returned by {@link #getType getType()} |
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| 74 | * indicating a data packet. |
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| 75 | ***/ |
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| 76 | public static final int DATA = 3; |
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| 77 | ||
| 78 | /*** |
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| 79 | * This is the actual TFTP spec |
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| 80 | * identifier and is equal to 4. |
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| 81 | * Identifier returned by {@link #getType getType()} |
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| 82 | * indicating an acknowledgement packet. |
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| 83 | ***/ |
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| 84 | public static final int ACKNOWLEDGEMENT = 4; |
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| 85 | ||
| 86 | /*** |
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| 87 | * This is the actual TFTP spec |
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| 88 | * identifier and is equal to 5. |
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| 89 | * Identifier returned by {@link #getType getType()} |
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| 90 | * indicating an error packet. |
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| 91 | ***/ |
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| 92 | public static final int ERROR = 5; |
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| 93 | ||
| 94 | /*** |
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| 95 | * The TFTP data packet maximum segment size in bytes. This is 512 |
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| 96 | * and is useful for those familiar with the TFTP protocol who want |
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| 97 | * to use the {@link org.apache.commons.net.tftp.TFTP} |
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| 98 | * class methods to implement their own TFTP servers or clients. |
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| 99 | ***/ |
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| 100 | public static final int SEGMENT_SIZE = 512; |
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| 101 | ||
| 102 | /*** The type of packet. ***/ |
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| 103 | int _type; |
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| 104 | ||
| 105 | /*** The port the packet came from or is going to. ***/ |
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| 106 | int _port; |
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| 107 | ||
| 108 | /*** The host the packet is going to be sent or where it came from. ***/ |
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| 109 | InetAddress _address; |
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| 110 | ||
| 111 | /*** |
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| 112 | * When you receive a datagram that you expect to be a TFTP packet, you use |
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| 113 | * this factory method to create the proper TFTPPacket object |
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| 114 | * encapsulating the data contained in that datagram. This method is the |
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| 115 | * only way you can instantiate a TFTPPacket derived class from a |
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| 116 | * datagram. |
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| 117 | * <p> |
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| 118 | * @param datagram The datagram containing a TFTP packet. |
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| 119 | * @return The TFTPPacket object corresponding to the datagram. |
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| 120 | * @exception TFTPPacketException If the datagram does not contain a valid |
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| 121 | * TFTP packet. |
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| 122 | ***/ |
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| 123 | public final static TFTPPacket newTFTPPacket(DatagramPacket datagram) |
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| 124 | throws TFTPPacketException |
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| 125 | { |
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| 126 | byte[] data; |
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| 127 | 0 | TFTPPacket packet = null; |
| 128 | ||
| 129 | 0 | if (datagram.getLength() < MIN_PACKET_SIZE) |
| 130 | 0 | throw new TFTPPacketException( |
| 131 | "Bad packet. Datagram data length is too short."); |
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| 132 | ||
| 133 | 0 | data = datagram.getData(); |
| 134 | ||
| 135 | 0 | switch (data[1]) |
| 136 | { |
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| 137 | case READ_REQUEST: |
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| 138 | 0 | packet = new TFTPReadRequestPacket(datagram); |
| 139 | 0 | break; |
| 140 | case WRITE_REQUEST: |
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| 141 | 0 | packet = new TFTPWriteRequestPacket(datagram); |
| 142 | 0 | break; |
| 143 | case DATA: |
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| 144 | 0 | packet = new TFTPDataPacket(datagram); |
| 145 | 0 | break; |
| 146 | case ACKNOWLEDGEMENT: |
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| 147 | 0 | packet = new TFTPAckPacket(datagram); |
| 148 | 0 | break; |
| 149 | case ERROR: |
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| 150 | 0 | packet = new TFTPErrorPacket(datagram); |
| 151 | 0 | break; |
| 152 | default: |
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| 153 | 0 | throw new TFTPPacketException( |
| 154 | "Bad packet. Invalid TFTP operator code."); |
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| 155 | } |
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| 156 | ||
| 157 | 0 | return packet; |
| 158 | } |
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| 159 | ||
| 160 | /*** |
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| 161 | * This constructor is not visible outside of the package. It is used |
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| 162 | * by subclasses within the package to initialize base data. |
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| 163 | * <p> |
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| 164 | * @param type The type of the packet. |
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| 165 | * @param address The host the packet came from or is going to be sent. |
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| 166 | * @param port The port the packet came from or is going to be sent. |
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| 167 | **/ |
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| 168 | TFTPPacket(int type, InetAddress address, class="keyword">int port) |
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| 169 | 0 | { |
| 170 | 0 | _type = type; |
| 171 | 0 | _address = address; |
| 172 | 0 | _port = port; |
| 173 | 0 | } |
| 174 | ||
| 175 | /*** |
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| 176 | * This is an abstract method only available within the package for |
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| 177 | * implementing efficient datagram transport by elminating buffering. |
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| 178 | * It takes a datagram as an argument, and a byte buffer in which |
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| 179 | * to store the raw datagram data. Inside the method, the data |
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| 180 | * should be set as the datagram's data and the datagram returned. |
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| 181 | * <p> |
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| 182 | * @param datagram The datagram to create. |
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| 183 | * @param data The buffer to store the packet and to use in the datagram. |
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| 184 | * @return The datagram argument. |
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| 185 | ***/ |
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| 186 | abstract DatagramPacket _newDatagram(DatagramPacket datagram, byte[] data); |
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| 187 | ||
| 188 | /*** |
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| 189 | * Creates a UDP datagram containing all the TFTP packet |
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| 190 | * data in the proper format. |
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| 191 | * This is an abstract method, exposed to the programmer in case he |
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| 192 | * wants to implement his own TFTP client instead of using |
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| 193 | * the {@link org.apache.commons.net.tftp.TFTPClient} |
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| 194 | * class. |
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| 195 | * Under normal circumstances, you should not have a need to call this |
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| 196 | * method. |
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| 197 | * <p> |
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| 198 | * @return A UDP datagram containing the TFTP packet. |
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| 199 | ***/ |
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| 200 | public abstract DatagramPacket newDatagram(); |
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| 201 | ||
| 202 | /*** |
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| 203 | * Returns the type of the packet. |
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| 204 | * <p> |
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| 205 | * @return The type of the packet. |
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| 206 | ***/ |
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| 207 | public final int getType() |
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| 208 | { |
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| 209 | 0 | return _type; |
| 210 | } |
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| 211 | ||
| 212 | /*** |
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| 213 | * Returns the address of the host where the packet is going to be sent |
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| 214 | * or where it came from. |
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| 215 | * <p> |
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| 216 | * @return The type of the packet. |
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| 217 | ***/ |
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| 218 | public final InetAddress getAddress() |
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| 219 | { |
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| 220 | 0 | return _address; |
| 221 | } |
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| 222 | ||
| 223 | /*** |
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| 224 | * Returns the port where the packet is going to be sent |
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| 225 | * or where it came from. |
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| 226 | * <p> |
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| 227 | * @return The port where the packet came from or where it is going. |
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| 228 | ***/ |
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| 229 | public final int getPort() |
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| 230 | { |
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| 231 | 0 | return _port; |
| 232 | } |
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| 233 | ||
| 234 | /*** Sets the port where the packet is going to be sent. ***/ |
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| 235 | public final void setPort(int port) |
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| 236 | { |
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| 237 | 0 | _port = port; |
| 238 | 0 | } |
| 239 | ||
| 240 | /*** Sets the host address where the packet is going to be sent. ***/ |
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| 241 | public final void setAddress(InetAddress address) |
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| 242 | { |
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| 243 | 0 | _address = address; |
| 244 | 0 | } |
| 245 | } |
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