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.time; 019 020import java.io.IOException; 021import java.net.DatagramPacket; 022import java.net.InetAddress; 023import java.util.Date; 024 025import org.apache.commons.net.DatagramSocketClient; 026 027/** 028 * The TimeUDPClient class is a UDP implementation of a client for the 029 * Time protocol described in RFC 868. To use the class, merely 030 * open a local datagram socket with 031 * {@link org.apache.commons.net.DatagramSocketClient#open open } 032 * and call {@link #getTime getTime } or 033 * {@link #getTime getDate } to retrieve the time. Then call 034 * {@link org.apache.commons.net.DatagramSocketClient#close close } 035 * to close the connection properly. Unlike 036 * {@link org.apache.commons.net.time.TimeTCPClient}, 037 * successive calls to {@link #getTime getTime } or 038 * {@link #getDate getDate } are permitted 039 * without re-establishing a connection. That is because UDP is a 040 * connectionless protocol and the Time protocol is stateless. 041 * 042 * 043 * @see TimeTCPClient 044 */ 045 046public final class TimeUDPClient extends DatagramSocketClient 047{ 048 /** The default time port. It is set to 37 according to RFC 868. */ 049 public static final int DEFAULT_PORT = 37; 050 051 /** 052 * The number of seconds between 00:00 1 January 1900 and 053 * 00:00 1 January 1970. This value can be useful for converting 054 * time values to other formats. 055 */ 056 public static final long SECONDS_1900_TO_1970 = 2208988800L; 057 058 private final byte[] dummyData = new byte[1]; 059 private final byte[] timeData = new byte[4]; 060 061 /** 062 * Retrieves the time from the specified server and port and 063 * returns it. The time is the number of seconds since 064 * 00:00 (midnight) 1 January 1900 GMT, as specified by RFC 868. 065 * This method reads the raw 32-bit big-endian 066 * unsigned integer from the server, converts it to a Java long, and 067 * returns the value. 068 * 069 * @param host The address of the server. 070 * @param port The port of the service. 071 * @return The time value retrieved from the server. 072 * @throws IOException If an error occurs while retrieving the time. 073 */ 074 public long getTime(final InetAddress host, final int port) throws IOException 075 { 076 long time; 077 final DatagramPacket sendPacket; 078 final DatagramPacket receivePacket; 079 080 sendPacket = 081 new DatagramPacket(dummyData, dummyData.length, host, port); 082 receivePacket = new DatagramPacket(timeData, timeData.length); 083 084 _socket_.send(sendPacket); 085 _socket_.receive(receivePacket); 086 087 time = 0L; 088 time |= (((timeData[0] & 0xff) << 24) & 0xffffffffL); 089 time |= (((timeData[1] & 0xff) << 16) & 0xffffffffL); 090 time |= (((timeData[2] & 0xff) << 8) & 0xffffffffL); 091 time |= ((timeData[3] & 0xff) & 0xffffffffL); 092 093 return time; 094 } 095 096 /** Same as <code> getTime(host, DEFAULT_PORT); </code> 097 * @param host the time server 098 * @return the time returned from the server 099 * @throws IOException on error 100 */ 101 public long getTime(final InetAddress host) throws IOException 102 { 103 return getTime(host, DEFAULT_PORT); 104 } 105 106 107 /** 108 * Retrieves the time from the server and returns a Java Date 109 * containing the time converted to the local time zone. 110 * 111 * @param host The address of the server. 112 * @param port The port of the service. 113 * @return A Date value containing the time retrieved from the server 114 * converted to the local time zone. 115 * @throws IOException If an error occurs while fetching the time. 116 */ 117 public Date getDate(final InetAddress host, final int port) throws IOException 118 { 119 return new Date((getTime(host, port) - SECONDS_1900_TO_1970)*1000L); 120 } 121 122 123 /** Same as <code> getTime(host, DEFAULT_PORT); </code> 124 * @param host the time server 125 * @return the date 126 * @throws IOException on error 127 */ 128 public Date getDate(final InetAddress host) throws IOException 129 { 130 return new Date((getTime(host, DEFAULT_PORT) - 131 SECONDS_1900_TO_1970)*1000L); 132 } 133 134} 135