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.time; 19 20 import java.io.IOException; 21 import java.net.DatagramPacket; 22 import java.net.InetAddress; 23 import java.util.Date; 24 25 import org.apache.commons.net.DatagramSocketClient; 26 27 /*** 28 * The TimeUDPClient class is a UDP implementation of a client for the 29 * Time protocol described in RFC 868. To use the class, merely 30 * open a local datagram socket with 31 * {@link org.apache.commons.net.DatagramSocketClient#open open } 32 * and call {@link #getTime getTime } or 33 * {@link #getTime getDate } to retrieve the time. Then call 34 * {@link org.apache.commons.net.DatagramSocketClient#close close } 35 * to close the connection properly. Unlike 36 * {@link org.apache.commons.net.time.TimeTCPClient}, 37 * successive calls to {@link #getTime getTime } or 38 * {@link #getDate getDate } are permitted 39 * without re-establishing a connection. That is because UDP is a 40 * connectionless protocol and the Time protocol is stateless. 41 * <p> 42 * <p> 43 * @see TimeTCPClient 44 ***/ 45 46 public final class TimeUDPClient extends DatagramSocketClient 47 { 48 /*** The default time port. It is set to 37 according to RFC 868. ***/ 49 public static final int DEFAULT_PORT = 37; 50 51 /*** 52 * The number of seconds between 00:00 1 January 1900 and 53 * 00:00 1 January 1970. This value can be useful for converting 54 * time values to other formats. 55 ***/ 56 public static final long SECONDS_1900_TO_1970 = 2208988800L; 57 58 private final byte[] __dummyData = new byte[1]; 59 private final byte[] __timeData = new byte[4]; 60 61 /*** 62 * Retrieves the time from the specified server and port and 63 * returns it. The time is the number of seconds since 64 * 00:00 (midnight) 1 January 1900 GMT, as specified by RFC 868. 65 * This method reads the raw 32-bit big-endian 66 * unsigned integer from the server, converts it to a Java long, and 67 * returns the value. 68 * <p> 69 * @param host The address of the server. 70 * @param port The port of the service. 71 * @return The time value retrieved from the server. 72 * @exception IOException If an error occurs while retrieving the time. 73 ***/ 74 public long getTime(InetAddress host, int port) throws IOException 75 { 76 long time; 77 DatagramPacket sendPacket, receivePacket; 78 79 sendPacket = 80 new DatagramPacket(__dummyData, __dummyData.length, host, port); 81 receivePacket = new DatagramPacket(__timeData, __timeData.length); 82 83 _socket_.send(sendPacket); 84 _socket_.receive(receivePacket); 85 86 time = 0L; 87 time |= (((__timeData[0] & 0xff) << 24) & 0xffffffffL); 88 time |= (((__timeData[1] & 0xff) << 16) & 0xffffffffL); 89 time |= (((__timeData[2] & 0xff) << 8) & 0xffffffffL); 90 time |= ((__timeData[3] & 0xff) & 0xffffffffL); 91 92 return time; 93 } 94 95 /*** Same as <code> getTime(host, DEFAULT_PORT); </code> ***/ 96 public long getTime(InetAddress host) throws IOException 97 { 98 return getTime(host, DEFAULT_PORT); 99 } 100 101 102 /*** 103 * Retrieves the time from the server and returns a Java Date 104 * containing the time converted to the local timezone. 105 * <p> 106 * @param host The address of the server. 107 * @param port The port of the service. 108 * @return A Date value containing the time retrieved from the server 109 * converted to the local timezone. 110 * @exception IOException If an error occurs while fetching the time. 111 ***/ 112 public Date getDate(InetAddress host, int port) throws IOException 113 { 114 return new Date((getTime(host, port) - SECONDS_1900_TO_1970)*1000L); 115 } 116 117 118 /*** Same as <code> getTime(host, DEFAULT_PORT); </code> ***/ 119 public Date getDate(InetAddress host) throws IOException 120 { 121 return new Date((getTime(host, DEFAULT_PORT) - 122 SECONDS_1900_TO_1970)*1000L); 123 } 124 125 } 126