001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018 package org.apache.commons.net.daytime;
019
020 import java.io.IOException;
021 import java.net.DatagramPacket;
022 import java.net.InetAddress;
023
024 import org.apache.commons.net.DatagramSocketClient;
025
026 /***
027 * The DaytimeUDPClient class is a UDP implementation of a client for the
028 * Daytime protocol described in RFC 867. To use the class, merely
029 * open a local datagram socket with
030 * {@link org.apache.commons.net.DatagramSocketClient#open open }
031 * and call {@link #getTime getTime } to retrieve the daytime
032 * string, then
033 * call {@link org.apache.commons.net.DatagramSocketClient#close close }
034 * to close the connection properly. Unlike
035 * {@link org.apache.commons.net.daytime.DaytimeTCPClient},
036 * successive calls to {@link #getTime getTime } are permitted
037 * without re-establishing a connection. That is because UDP is a
038 * connectionless protocol and the Daytime protocol is stateless.
039 * <p>
040 * <p>
041 * @author Daniel F. Savarese
042 * @see DaytimeTCPClient
043 ***/
044
045 public final class DaytimeUDPClient extends DatagramSocketClient
046 {
047 /*** The default daytime port. It is set to 13 according to RFC 867. ***/
048 public static final int DEFAULT_PORT = 13;
049
050 private byte[] __dummyData = new byte[1];
051 // Received dates should be less than 256 bytes
052 private byte[] __timeData = new byte[256];
053
054 /***
055 * Retrieves the time string from the specified server and port and
056 * returns it.
057 * <p>
058 * @param host The address of the server.
059 * @param port The port of the service.
060 * @return The time string.
061 * @exception IOException If an error occurs while retrieving the time.
062 ***/
063 public String getTime(InetAddress host, int port) throws IOException
064 {
065 DatagramPacket sendPacket, receivePacket;
066
067 sendPacket =
068 new DatagramPacket(__dummyData, __dummyData.length, host, port);
069 receivePacket = new DatagramPacket(__timeData, __timeData.length);
070
071 _socket_.send(sendPacket);
072 _socket_.receive(receivePacket);
073
074 return new String(receivePacket.getData(), 0, receivePacket.getLength());
075 }
076
077 /*** Same as <code>getTime(host, DaytimeUDPClient.DEFAULT_PORT);</code> ***/
078 public String getTime(InetAddress host) throws IOException
079 {
080 return getTime(host, DEFAULT_PORT);
081 }
082
083 }
084