001 /*
002 * Copyright 2001-2005 The Apache Software Foundation
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016 package org.apache.commons.net.tftp;
017
018 import java.net.DatagramPacket;
019 import java.net.InetAddress;
020
021 /***
022 * A final class derived from TFTPPacket definiing the TFTP Acknowledgement
023 * packet type.
024 * <p>
025 * Details regarding the TFTP protocol and the format of TFTP packets can
026 * be found in RFC 783. But the point of these classes is to keep you
027 * from having to worry about the internals. Additionally, only very
028 * few people should have to care about any of the TFTPPacket classes
029 * or derived classes. Almost all users should only be concerned with the
030 * {@link org.apache.commons.net.tftp.TFTPClient} class
031 * {@link org.apache.commons.net.tftp.TFTPClient#receiveFile receiveFile()}
032 * and
033 * {@link org.apache.commons.net.tftp.TFTPClient#sendFile sendFile()}
034 * methods.
035 * <p>
036 * <p>
037 * @author Daniel F. Savarese
038 * @see TFTPPacket
039 * @see TFTPPacketException
040 * @see TFTP
041 ***/
042
043 public final class TFTPAckPacket extends TFTPPacket
044 {
045 /*** The block number being acknowledged by the packet. ***/
046 int _blockNumber;
047
048 /***
049 * Creates an acknowledgment packet to be sent to a host at a given port
050 * acknowledging receipt of a block.
051 * <p>
052 * @param destination The host to which the packet is going to be sent.
053 * @param port The port to which the packet is going to be sent.
054 * @param blockNumber The block number being acknowledged.
055 ***/
056 public TFTPAckPacket(InetAddress destination, int port, int blockNumber)
057 {
058 super(TFTPPacket.ACKNOWLEDGEMENT, destination, port);
059 _blockNumber = blockNumber;
060 }
061
062 /***
063 * Creates an acknowledgement packet based from a received
064 * datagram. Assumes the datagram is at least length 4, else an
065 * ArrayIndexOutOfBoundsException may be thrown.
066 * <p>
067 * @param datagram The datagram containing the received acknowledgement.
068 * @throws TFTPPacketException If the datagram isn't a valid TFTP
069 * acknowledgement packet.
070 ***/
071 TFTPAckPacket(DatagramPacket datagram) throws TFTPPacketException
072 {
073 super(TFTPPacket.ACKNOWLEDGEMENT, datagram.getAddress(),
074 datagram.getPort());
075 byte[] data;
076
077 data = datagram.getData();
078
079 if (getType() != data[1])
080 throw new TFTPPacketException("TFTP operator code does not match type.");
081
082 _blockNumber = (((data[2] & 0xff) << 8) | (data[3] & 0xff));
083 }
084
085 /***
086 * This is a method only available within the package for
087 * implementing efficient datagram transport by elminating buffering.
088 * It takes a datagram as an argument, and a byte buffer in which
089 * to store the raw datagram data. Inside the method, the data
090 * is set as the datagram's data and the datagram returned.
091 * <p>
092 * @param datagram The datagram to create.
093 * @param data The buffer to store the packet and to use in the datagram.
094 * @return The datagram argument.
095 ***/
096 DatagramPacket _newDatagram(DatagramPacket datagram, byte[] data)
097 {
098 data[0] = 0;
099 data[1] = (byte)_type;
100 data[2] = (byte)((_blockNumber & 0xffff) >> 8);
101 data[3] = (byte)(_blockNumber & 0xff);
102
103 datagram.setAddress(_address);
104 datagram.setPort(_port);
105 datagram.setData(data);
106 datagram.setLength(4);
107
108 return datagram;
109 }
110
111
112 /***
113 * Creates a UDP datagram containing all the TFTP
114 * acknowledgement packet data in the proper format.
115 * This is a method exposed to the programmer in case he
116 * wants to implement his own TFTP client instead of using
117 * the {@link org.apache.commons.net.tftp.TFTPClient}
118 * class. Under normal circumstances, you should not have a need to call this
119 * method.
120 * <p>
121 * @return A UDP datagram containing the TFTP acknowledgement packet.
122 ***/
123 public DatagramPacket newDatagram()
124 {
125 byte[] data;
126
127 data = new byte[4];
128 data[0] = 0;
129 data[1] = (byte)_type;
130 data[2] = (byte)((_blockNumber & 0xffff) >> 8);
131 data[3] = (byte)(_blockNumber & 0xff);
132
133 return new DatagramPacket(data, data.length, _address, _port);
134 }
135
136
137 /***
138 * Returns the block number of the acknowledgement.
139 * <p>
140 * @return The block number of the acknowledgement.
141 ***/
142 public int getBlockNumber()
143 {
144 return _blockNumber;
145 }
146
147
148 /*** Sets the block number of the acknowledgement. ***/
149 public void setBlockNumber(int blockNumber)
150 {
151 _blockNumber = blockNumber;
152 }
153 }
154