1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16 package org.apache.commons.net.tftp;
17
18 import java.net.DatagramPacket;
19 import java.net.InetAddress;
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 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 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 _newDatagram(DatagramPacket 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 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