1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18 package org.apache.commons.net.daytime;
19
20 import java.io.IOException;
21 import java.net.DatagramPacket;
22 import java.net.InetAddress;
23
24 import org.apache.commons.net.DatagramSocketClient;
25
26 /**
27 * The DaytimeUDPClient class is a UDP implementation of a client for the
28 * Daytime protocol described in RFC 867. To use the class, merely
29 * open a local datagram socket with
30 * {@link org.apache.commons.net.DatagramSocketClient#open open }
31 * and call {@link #getTime getTime } to retrieve the daytime
32 * string, then
33 * call {@link org.apache.commons.net.DatagramSocketClient#close close }
34 * to close the connection properly. Unlike
35 * {@link org.apache.commons.net.daytime.DaytimeTCPClient},
36 * successive calls to {@link #getTime getTime } are permitted
37 * without re-establishing a connection. That is because UDP is a
38 * connectionless protocol and the Daytime protocol is stateless.
39 * @see DaytimeTCPClient
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 final byte[] __dummyData = new byte[1];
47 // Received dates should be less than 256 bytes
48 private final 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(), this.getCharset());
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