001: /*
002: * Copyright 2001-2005 The Apache Software Foundation
003: *
004: * Licensed under the Apache License, Version 2.0 (the "License");
005: * you may not use this file except in compliance with the License.
006: * You may obtain a copy of the License at
007: *
008: * http://www.apache.org/licenses/LICENSE-2.0
009: *
010: * Unless required by applicable law or agreed to in writing, software
011: * distributed under the License is distributed on an "AS IS" BASIS,
012: * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013: * See the License for the specific language governing permissions and
014: * limitations under the License.
015: */
016: package org.apache.commons.net;
017:
018: import java.io.IOException;
019: import java.net.DatagramPacket;
020: import java.net.InetAddress;
021: import java.util.Date;
022:
023: /***
024: * The TimeUDPClient class is a UDP implementation of a client for the
025: * Time protocol described in RFC 868. To use the class, merely
026: * open a local datagram socket with
027: * {@link org.apache.commons.net.DatagramSocketClient#open open }
028: * and call {@link #getTime getTime } or
029: * {@link #getTime getDate } to retrieve the time. Then call
030: * {@link org.apache.commons.net.DatagramSocketClient#close close }
031: * to close the connection properly. Unlike
032: * {@link org.apache.commons.net.TimeTCPClient},
033: * successive calls to {@link #getTime getTime } or
034: * {@link #getDate getDate } are permitted
035: * without re-establishing a connection. That is because UDP is a
036: * connectionless protocol and the Time protocol is stateless.
037: * <p>
038: * <p>
039: * @author Daniel F. Savarese
040: * @see TimeTCPClient
041: ***/
042:
043: public final class TimeUDPClient extends DatagramSocketClient {
044: /*** The default time port. It is set to 37 according to RFC 868. ***/
045: public static final int DEFAULT_PORT = 37;
046:
047: /***
048: * The number of seconds between 00:00 1 January 1900 and
049: * 00:00 1 January 1970. This value can be useful for converting
050: * time values to other formats.
051: ***/
052: public static final long SECONDS_1900_TO_1970 = 2208988800L;
053:
054: private byte[] __dummyData = new byte[1];
055: private byte[] __timeData = new byte[4];
056:
057: /***
058: * Retrieves the time from the specified server and port and
059: * returns it. The time is the number of seconds since
060: * 00:00 (midnight) 1 January 1900 GMT, as specified by RFC 868.
061: * This method reads the raw 32-bit big-endian
062: * unsigned integer from the server, converts it to a Java long, and
063: * returns the value.
064: * <p>
065: * @param host The address of the server.
066: * @param port The port of the service.
067: * @return The time value retrieved from the server.
068: * @exception IOException If an error occurs while retrieving the time.
069: ***/
070: public long getTime(InetAddress host, int port) throws IOException {
071: long time;
072: DatagramPacket sendPacket, receivePacket;
073:
074: sendPacket = new DatagramPacket(__dummyData,
075: __dummyData.length, host, port);
076: receivePacket = new DatagramPacket(__timeData,
077: __timeData.length);
078:
079: _socket_.send(sendPacket);
080: _socket_.receive(receivePacket);
081:
082: time = 0L;
083: time |= (((__timeData[0] & 0xff) << 24) & 0xffffffffL);
084: time |= (((__timeData[1] & 0xff) << 16) & 0xffffffffL);
085: time |= (((__timeData[2] & 0xff) << 8) & 0xffffffffL);
086: time |= ((__timeData[3] & 0xff) & 0xffffffffL);
087:
088: return time;
089: }
090:
091: /*** Same as <code> getTime(host, DEFAULT_PORT); </code> ***/
092: public long getTime(InetAddress host) throws IOException {
093: return getTime(host, DEFAULT_PORT);
094: }
095:
096: /***
097: * Retrieves the time from the server and returns a Java Date
098: * containing the time converted to the local timezone.
099: * <p>
100: * @param host The address of the server.
101: * @param port The port of the service.
102: * @return A Date value containing the time retrieved from the server
103: * converted to the local timezone.
104: * @exception IOException If an error occurs while fetching the time.
105: ***/
106: public Date getDate(InetAddress host, int port) throws IOException {
107: return new Date(
108: (getTime(host, port) - SECONDS_1900_TO_1970) * 1000L);
109: }
110:
111: /*** Same as <code> getTime(host, DEFAULT_PORT); </code> ***/
112: public Date getDate(InetAddress host) throws IOException {
113: return new Date(
114: (getTime(host, DEFAULT_PORT) - SECONDS_1900_TO_1970) * 1000L);
115: }
116:
117: }
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