1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16 package org.apache.commons.net;
17
18 import java.io.IOException;
19 import java.net.DatagramPacket;
20 import java.net.InetAddress;
21
22 /***
23 * The DaytimeUDPClient class is a UDP implementation of a client for the
24 * Daytime protocol described in RFC 867. To use the class, merely
25 * open a local datagram socket with
26 * {@link org.apache.commons.net.DatagramSocketClient#open open }
27 * and call {@link #getTime getTime } to retrieve the daytime
28 * string, then
29 * call {@link org.apache.commons.net.DatagramSocketClient#close close }
30 * to close the connection properly. Unlike
31 * {@link org.apache.commons.net.DaytimeTCPClient},
32 * successive calls to {@link #getTime getTime } are permitted
33 * without re-establishing a connection. That is because UDP is a
34 * connectionless protocol and the Daytime protocol is stateless.
35 * <p>
36 * <p>
37 * @author Daniel F. Savarese
38 * @see DaytimeTCPClient
39 ***/
40
41 public final class DaytimeUDPClient extends DatagramSocketClient
42 {
43 /*** The default daytime port. It is set to 13 according to RFC 867. ***/
44 public static final int DEFAULT_PORT = 13;
45
46 private byte[] __dummyData = new byte[1];
47
48 private byte[] __timeData = new byte[256];
49
50 /***
51 * Retrieves the time string from the specified server and port and
52 * returns it.
53 * <p>
54 * @param host The address of the server.
55 * @param port The port of the service.
56 * @return The time string.
57 * @exception IOException If an error occurs while retrieving the time.
58 ***/
59 public String getTime(InetAddress host, int port) throws IOException
60 {
61 DatagramPacket sendPacket, receivePacket;
62
63 sendPacket =
64 new DatagramPacket(__dummyData, __dummyData.length, host, port);
65 receivePacket = new DatagramPacket(__timeData, __timeData.length);
66
67 _socket_.send(sendPacket);
68 _socket_.receive(receivePacket);
69
70 return new String(receivePacket.getData(), 0, receivePacket.getLength());
71 }
72
73 /*** Same as <code>getTime(host, DaytimeUDPClient.DEFAULT_PORT);</code> ***/
74 public String getTime(InetAddress host) throws IOException
75 {
76 return getTime(host, DEFAULT_PORT);
77 }
78
79 }
80