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 Daytime protocol described in RFC 867. To use the class, merely open a local datagram
28 * socket with {@link org.apache.commons.net.DatagramSocketClient#open open } and call {@link #getTime getTime } to retrieve the daytime string, then call
29 * {@link org.apache.commons.net.DatagramSocketClient#close close } to close the connection properly. Unlike
30 * {@link org.apache.commons.net.daytime.DaytimeTCPClient}, successive calls to {@link #getTime getTime } are permitted without re-establishing a connection.
31 * That is because UDP is a connectionless protocol and the Daytime protocol is stateless.
32 *
33 * @see DaytimeTCPClient
34 */
35 public final class DaytimeUDPClient extends DatagramSocketClient {
36 /** The default daytime port. It is set to 13 according to RFC 867. */
37 public static final int DEFAULT_PORT = 13;
38
39 private final byte[] dummyData = new byte[1];
40 // Received dates should be less than 256 bytes
41 private final byte[] timeData = new byte[256];
42
43 /**
44 * Same as <code>getTime(host, DaytimeUDPClient.DEFAULT_PORT);</code>
45 *
46 * @param host the host
47 * @return the time
48 * @throws IOException on error
49 */
50 public String getTime(final InetAddress host) throws IOException {
51 return getTime(host, DEFAULT_PORT);
52 }
53
54 /**
55 * Retrieves the time string from the specified server and port and returns it.
56 *
57 * @param host The address of the server.
58 * @param port The port of the service.
59 * @return The time string.
60 * @throws IOException If an error occurs while retrieving the time.
61 */
62 public String getTime(final InetAddress host, final int port) throws IOException {
63 final DatagramPacket sendPacket;
64 final DatagramPacket receivePacket;
65
66 sendPacket = new DatagramPacket(dummyData, dummyData.length, host, port);
67 receivePacket = new DatagramPacket(timeData, timeData.length);
68
69 checkOpen().send(sendPacket);
70 checkOpen().receive(receivePacket);
71
72 return new String(receivePacket.getData(), 0, receivePacket.getLength(), getCharset()); // Java 1.6 can use getCharset()
73 }
74
75 }