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Java > Open Source Codes > org > apache > commons > net > tftp > TFTPAckPacket


1 /*
2  * Copyright 2001-2005 The Apache Software Foundation
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package org.apache.commons.net.tftp;
17
18 import java.net.DatagramPacket JavaDoc;
19 import java.net.InetAddress JavaDoc;
20
21 /***
22  * A final class derived from TFTPPacket definiing the TFTP Acknowledgement
23  * packet type.
24  * <p>
25  * Details regarding the TFTP protocol and the format of TFTP packets can
26  * be found in RFC 783. But the point of these classes is to keep you
27  * from having to worry about the internals. Additionally, only very
28  * few people should have to care about any of the TFTPPacket classes
29  * or derived classes. Almost all users should only be concerned with the
30  * {@link org.apache.commons.net.tftp.TFTPClient} class
31  * {@link org.apache.commons.net.tftp.TFTPClient#receiveFile receiveFile()}
32  * and
33  * {@link org.apache.commons.net.tftp.TFTPClient#sendFile sendFile()}
34  * methods.
35  * <p>
36  * <p>
37  * @author Daniel F. Savarese
38  * @see TFTPPacket
39  * @see TFTPPacketException
40  * @see TFTP
41  ***/
42
43 public final class TFTPAckPacket extends TFTPPacket
44 {
45     /*** The block number being acknowledged by the packet. ***/
46     int _blockNumber;
47
48     /***
49      * Creates an acknowledgment packet to be sent to a host at a given port
50      * acknowledging receipt of a block.
51      * <p>
52      * @param destination The host to which the packet is going to be sent.
53      * @param port The port to which the packet is going to be sent.
54      * @param blockNumber The block number being acknowledged.
55      ***/
56     public TFTPAckPacket(InetAddress JavaDoc destination, int port, int blockNumber)
57     {
58         super(TFTPPacket.ACKNOWLEDGEMENT, destination, port);
59         _blockNumber = blockNumber;
60     }
61
62     /***
63      * Creates an acknowledgement packet based from a received
64      * datagram. Assumes the datagram is at least length 4, else an
65      * ArrayIndexOutOfBoundsException may be thrown.
66      * <p>
67      * @param datagram The datagram containing the received acknowledgement.
68      * @throws TFTPPacketException If the datagram isn't a valid TFTP
69      * acknowledgement packet.
70      ***/
71     TFTPAckPacket(DatagramPacket JavaDoc datagram) throws TFTPPacketException
72     {
73         super(TFTPPacket.ACKNOWLEDGEMENT, datagram.getAddress(),
74               datagram.getPort());
75         byte[] data;
76
77         data = datagram.getData();
78
79         if (getType() != data[1])
80             throw new TFTPPacketException("TFTP operator code does not match type.");
81
82         _blockNumber = (((data[2] & 0xff) << 8) | (data[3] & 0xff));
83     }
84
85     /***
86      * This is a method only available within the package for
87      * implementing efficient datagram transport by elminating buffering.
88      * It takes a datagram as an argument, and a byte buffer in which
89      * to store the raw datagram data. Inside the method, the data
90      * is set as the datagram's data and the datagram returned.
91      * <p>
92      * @param datagram The datagram to create.
93      * @param data The buffer to store the packet and to use in the datagram.
94      * @return The datagram argument.
95      ***/
96     DatagramPacket JavaDoc _newDatagram(DatagramPacket JavaDoc datagram, byte[] data)
97     {
98         data[0] = 0;
99         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 JavaDoc 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 JavaDoc(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
155
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