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 018package org.apache.commons.net.daytime; 019 020import java.io.IOException; 021import java.net.DatagramPacket; 022import java.net.InetAddress; 023 024import org.apache.commons.net.DatagramSocketClient; 025 026/** 027 * 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 028 * socket with {@link org.apache.commons.net.DatagramSocketClient#open open } and call {@link #getTime getTime } to retrieve the daytime string, then call 029 * {@link org.apache.commons.net.DatagramSocketClient#close close } to close the connection properly. Unlike 030 * {@link org.apache.commons.net.daytime.DaytimeTCPClient}, successive calls to {@link #getTime getTime } are permitted without re-establishing a connection. 031 * That is because UDP is a connectionless protocol and the Daytime protocol is stateless. 032 * 033 * @see DaytimeTCPClient 034 */ 035public final class DaytimeUDPClient extends DatagramSocketClient { 036 /** The default daytime port. It is set to 13 according to RFC 867. */ 037 public static final int DEFAULT_PORT = 13; 038 039 private final byte[] dummyData = new byte[1]; 040 // Received dates should be less than 256 bytes 041 private final byte[] timeData = new byte[256]; 042 043 /** 044 * Same as <code>getTime(host, DaytimeUDPClient.DEFAULT_PORT);</code> 045 * 046 * @param host the host 047 * @return the time 048 * @throws IOException on error 049 */ 050 public String getTime(final InetAddress host) throws IOException { 051 return getTime(host, DEFAULT_PORT); 052 } 053 054 /** 055 * Retrieves the time string from the specified server and port and returns it. 056 * 057 * @param host The address of the server. 058 * @param port The port of the service. 059 * @return The time string. 060 * @throws IOException If an error occurs while retrieving the time. 061 */ 062 public String getTime(final InetAddress host, final int port) throws IOException { 063 final DatagramPacket sendPacket; 064 final DatagramPacket receivePacket; 065 066 sendPacket = new DatagramPacket(dummyData, dummyData.length, host, port); 067 receivePacket = new DatagramPacket(timeData, timeData.length); 068 069 checkOpen().send(sendPacket); 070 checkOpen().receive(receivePacket); 071 072 return new String(receivePacket.getData(), 0, receivePacket.getLength(), getCharset()); // Java 1.6 can use getCharset() 073 } 074 075}