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 final byte[] __dummyData = new byte[1]; 051 // Received dates should be less than 256 bytes 052 private final 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