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 Time protocol described in RFC 868. To use the class, merely open a local datagram socket 029 * with {@link org.apache.commons.net.DatagramSocketClient#open open } and call {@link #getTime getTime } or {@link #getTime getDate } to retrieve the time. 030 * Then call {@link org.apache.commons.net.DatagramSocketClient#close close } to close the connection properly. Unlike 031 * {@link org.apache.commons.net.time.TimeTCPClient}, successive calls to {@link #getTime getTime } or {@link #getDate getDate } are permitted without 032 * re-establishing a connection. That is because UDP is a connectionless protocol and the Time protocol is stateless. 033 * 034 * 035 * @see TimeTCPClient 036 */ 037 038public final class TimeUDPClient extends DatagramSocketClient { 039 /** The default time port. It is set to 37 according to RFC 868. */ 040 public static final int DEFAULT_PORT = 37; 041 042 /** 043 * 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. 044 */ 045 public static final long SECONDS_1900_TO_1970 = 2208988800L; 046 047 private final byte[] dummyData = new byte[1]; 048 private final byte[] timeData = new byte[4]; 049 050 /** 051 * Same as <code> getTime(host, DEFAULT_PORT); </code> 052 * 053 * @param host the time-server 054 * @return the date 055 * @throws IOException on error 056 */ 057 public Date getDate(final InetAddress host) throws IOException { 058 return new Date((getTime(host, DEFAULT_PORT) - SECONDS_1900_TO_1970) * 1000L); 059 } 060 061 /** 062 * Retrieves the time from the server and returns a Java Date containing the time converted to the local time zone. 063 * 064 * @param host The address of the server. 065 * @param port The port of the service. 066 * @return A Date value containing the time retrieved from the server converted to the local time zone. 067 * @throws IOException If an error occurs while fetching the time. 068 */ 069 public Date getDate(final InetAddress host, final int port) throws IOException { 070 return new Date((getTime(host, port) - SECONDS_1900_TO_1970) * 1000L); 071 } 072 073 /** 074 * Same as <code> getTime(host, DEFAULT_PORT); </code> 075 * 076 * @param host the time-server 077 * @return the time returned from the server 078 * @throws IOException on error 079 */ 080 public long getTime(final InetAddress host) throws IOException { 081 return getTime(host, DEFAULT_PORT); 082 } 083 084 /** 085 * Retrieves the time from the specified server and port and returns it. The time is the number of seconds since 00:00 (midnight) 1 January 1900 GMT, as 086 * 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. 087 * 088 * @param host The address of the server. 089 * @param port The port of the service. 090 * @return The time value retrieved from the server. 091 * @throws IOException If an error occurs while retrieving the time. 092 */ 093 public long getTime(final InetAddress host, final int port) throws IOException { 094 final DatagramPacket sendPacket = new DatagramPacket(dummyData, dummyData.length, host, port); 095 final DatagramPacket receivePacket = new DatagramPacket(timeData, timeData.length); 096 097 checkOpen().send(sendPacket); 098 checkOpen().receive(receivePacket); 099 100 long time = 0L; 101 time |= (timeData[0] & 0xff) << 24 & 0xffffffffL; 102 time |= (timeData[1] & 0xff) << 16 & 0xffffffffL; 103 time |= (timeData[2] & 0xff) << 8 & 0xffffffffL; 104 time |= timeData[3] & 0xff & 0xffffffffL; 105 106 return time; 107 } 108 109}