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.time; 019 020 import java.io.IOException; 021 import java.net.DatagramPacket; 022 import java.net.InetAddress; 023 import java.util.Date; 024 025 import 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 * <p> 042 * <p> 043 * @author Daniel F. Savarese 044 * @see TimeTCPClient 045 ***/ 046 047 public final class TimeUDPClient extends DatagramSocketClient 048 { 049 /*** The default time port. It is set to 37 according to RFC 868. ***/ 050 public static final int DEFAULT_PORT = 37; 051 052 /*** 053 * The number of seconds between 00:00 1 January 1900 and 054 * 00:00 1 January 1970. This value can be useful for converting 055 * time values to other formats. 056 ***/ 057 public static final long SECONDS_1900_TO_1970 = 2208988800L; 058 059 private final byte[] __dummyData = new byte[1]; 060 private final byte[] __timeData = new byte[4]; 061 062 /*** 063 * Retrieves the time from the specified server and port and 064 * returns it. The time is the number of seconds since 065 * 00:00 (midnight) 1 January 1900 GMT, as specified by RFC 868. 066 * This method reads the raw 32-bit big-endian 067 * unsigned integer from the server, converts it to a Java long, and 068 * returns the value. 069 * <p> 070 * @param host The address of the server. 071 * @param port The port of the service. 072 * @return The time value retrieved from the server. 073 * @exception IOException If an error occurs while retrieving the time. 074 ***/ 075 public long getTime(InetAddress host, int port) throws IOException 076 { 077 long time; 078 DatagramPacket sendPacket, 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 public long getTime(InetAddress host) throws IOException 098 { 099 return getTime(host, DEFAULT_PORT); 100 } 101 102 103 /*** 104 * Retrieves the time from the server and returns a Java Date 105 * containing the time converted to the local timezone. 106 * <p> 107 * @param host The address of the server. 108 * @param port The port of the service. 109 * @return A Date value containing the time retrieved from the server 110 * converted to the local timezone. 111 * @exception IOException If an error occurs while fetching the time. 112 ***/ 113 public Date getDate(InetAddress host, int port) throws IOException 114 { 115 return new Date((getTime(host, port) - SECONDS_1900_TO_1970)*1000L); 116 } 117 118 119 /*** Same as <code> getTime(host, DEFAULT_PORT); </code> ***/ 120 public Date getDate(InetAddress host) throws IOException 121 { 122 return new Date((getTime(host, DEFAULT_PORT) - 123 SECONDS_1900_TO_1970)*1000L); 124 } 125 126 } 127