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 * @author Daniel F. Savarese 44 * @see TimeTCPClient 45 ***/ 46 47 public final class TimeUDPClient extends DatagramSocketClient 48 { 49 /*** The default time port. It is set to 37 according to RFC 868. ***/ 50 public static final int DEFAULT_PORT = 37; 51 52 /*** 53 * The number of seconds between 00:00 1 January 1900 and 54 * 00:00 1 January 1970. This value can be useful for converting 55 * time values to other formats. 56 ***/ 57 public static final long SECONDS_1900_TO_1970 = 2208988800L; 58 59 private byte[] __dummyData = new byte[1]; 60 private byte[] __timeData = new byte[4]; 61 62 /*** 63 * Retrieves the time from the specified server and port and 64 * returns it. The time is the number of seconds since 65 * 00:00 (midnight) 1 January 1900 GMT, as specified by RFC 868. 66 * This method reads the raw 32-bit big-endian 67 * unsigned integer from the server, converts it to a Java long, and 68 * returns the value. 69 * <p> 70 * @param host The address of the server. 71 * @param port The port of the service. 72 * @return The time value retrieved from the server. 73 * @exception IOException If an error occurs while retrieving the time. 74 ***/ 75 public long getTime(InetAddress host, int port) throws IOException 76 { 77 long time; 78 DatagramPacket sendPacket, receivePacket; 79 80 sendPacket = 81 new DatagramPacket(__dummyData, __dummyData.length, host, port); 82 receivePacket = new DatagramPacket(__timeData, __timeData.length); 83 84 _socket_.send(sendPacket); 85 _socket_.receive(receivePacket); 86 87 time = 0L; 88 time |= (((__timeData[0] & 0xff) << 24) & 0xffffffffL); 89 time |= (((__timeData[1] & 0xff) << 16) & 0xffffffffL); 90 time |= (((__timeData[2] & 0xff) << 8) & 0xffffffffL); 91 time |= ((__timeData[3] & 0xff) & 0xffffffffL); 92 93 return time; 94 } 95 96 /*** Same as <code> getTime(host, DEFAULT_PORT); </code> ***/ 97 public long getTime(InetAddress host) throws IOException 98 { 99 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