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