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Java > Open Source Codes > org > apache > commons > net > DaytimeUDPClient


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;
17
18 import java.io.IOException JavaDoc;
19 import java.net.DatagramPacket JavaDoc;
20 import java.net.InetAddress JavaDoc;
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     // Received dates should be less than 256 bytes
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 JavaDoc getTime(InetAddress JavaDoc host, int port) throws IOException JavaDoc
60     {
61         DatagramPacket JavaDoc sendPacket, receivePacket;
62
63         sendPacket =
64             new DatagramPacket JavaDoc(__dummyData, __dummyData.length, host, port);
65         receivePacket = new DatagramPacket JavaDoc(__timeData, __timeData.length);
66
67         _socket_.send(sendPacket);
68         _socket_.receive(receivePacket);
69
70         return new String JavaDoc(receivePacket.getData(), 0, receivePacket.getLength());
71     }
72
73     /*** Same as <code>getTime(host, DaytimeUDPClient.DEFAULT_PORT);</code> ***/
74     public String JavaDoc getTime(InetAddress JavaDoc host) throws IOException JavaDoc
75     {
76         return getTime(host, DEFAULT_PORT);
77     }
78
79 }
80
81
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