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 package org.apache.commons.net;
18
19 import java.io.IOException;
20 import java.net.DatagramPacket;
21 import java.net.InetAddress;
22
23 /***
24 * The DaytimeUDPClient class is a UDP implementation of a client for the
25 * Daytime protocol described in RFC 867. To use the class, merely
26 * open a local datagram socket with
27 * {@link org.apache.commons.net.DatagramSocketClient#open open }
28 * and call {@link #getTime getTime } to retrieve the daytime
29 * string, then
30 * call {@link org.apache.commons.net.DatagramSocketClient#close close }
31 * to close the connection properly. Unlike
32 * {@link org.apache.commons.net.DaytimeTCPClient},
33 * successive calls to {@link #getTime getTime } are permitted
34 * without re-establishing a connection. That is because UDP is a
35 * connectionless protocol and the Daytime protocol is stateless.
36 * <p>
37 * <p>
38 * @author Daniel F. Savarese
39 * @see DaytimeTCPClient
40 ***/
41
42 public final class DaytimeUDPClient extends DatagramSocketClient
43 {
44 /*** The default daytime port. It is set to 13 according to RFC 867. ***/
45 public static final int DEFAULT_PORT = 13;
46
47 private byte[] __dummyData = new byte[1];
48 // Received dates should be less than 256 bytes
49 private byte[] __timeData = new byte[256];
50
51 /***
52 * Retrieves the time string from the specified server and port and
53 * returns it.
54 * <p>
55 * @param host The address of the server.
56 * @param port The port of the service.
57 * @return The time string.
58 * @exception IOException If an error occurs while retrieving the time.
59 ***/
60 public String getTime(InetAddress host, int port) throws IOException
61 {
62 DatagramPacket sendPacket, receivePacket;
63
64 sendPacket =
65 new DatagramPacket(__dummyData, __dummyData.length, host, port);
66 receivePacket = new DatagramPacket(__timeData, __timeData.length);
67
68 _socket_.send(sendPacket);
69 _socket_.receive(receivePacket);
70
71 return new String(receivePacket.getData(), 0, receivePacket.getLength());
72 }
73
74 /*** Same as <code>getTime(host, DaytimeUDPClient.DEFAULT_PORT);</code> ***/
75 public String getTime(InetAddress host) throws IOException
76 {
77 return getTime(host, DEFAULT_PORT);
78 }
79
80 }
81