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 }