| package org.apache.commons.net.ntp; |
| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| |
| import java.io.IOException; |
| import java.net.DatagramPacket; |
| import java.net.InetAddress; |
| |
| import org.apache.commons.net.DatagramSocketClient; |
| |
| /*** |
| * The NTPUDPClient class is a UDP implementation of a client for the |
| * Network Time Protocol (NTP) described in RFC 1305 as well as the |
| * Simple Network Time Protocol (SNTP) in RFC-2030. To use the class, |
| * merely open a local datagram socket with <a href="#open"> open </a> |
| * and call <a href="#getTime"> getTime </a> to retrieve the time. Then call |
| * <a href="org.apache.commons.net.DatagramSocketClient.html#close"> close </a> |
| * to close the connection properly. |
| * Successive calls to <a href="#getTime"> getTime </a> are permitted |
| * without re-establishing a connection. That is because UDP is a |
| * connectionless protocol and the Network Time Protocol is stateless. |
| * |
| * @author Jason Mathews, MITRE Corp |
| * @version $Revision$ $Date$ |
| ***/ |
| |
| public final class NTPUDPClient extends DatagramSocketClient |
| { |
| /*** The default NTP port. It is set to 123 according to RFC 1305. ***/ |
| public static final int DEFAULT_PORT = 123; |
| |
| private int _version = NtpV3Packet.VERSION_3; |
| |
| /*** |
| * Retrieves the time information from the specified server and port and |
| * returns it. The time is the number of miliiseconds since |
| * 00:00 (midnight) 1 January 1900 UTC, as specified by RFC 1305. |
| * This method reads the raw NTP packet and constructs a <i>TimeInfo</i> |
| * object that allows access to all the fields of the NTP message header. |
| * <p> |
| * @param host The address of the server. |
| * @param port The port of the service. |
| * @return The time value retrieved from the server. |
| * @exception IOException If an error occurs while retrieving the time. |
| ***/ |
| public TimeInfo getTime(InetAddress host, int port) throws IOException |
| { |
| // if not connected then open to next available UDP port |
| if (!isOpen()) |
| { |
| open(); |
| } |
| |
| NtpV3Packet message = new NtpV3Impl(); |
| message.setMode(NtpV3Packet.MODE_CLIENT); |
| message.setVersion(_version); |
| DatagramPacket sendPacket = message.getDatagramPacket(); |
| sendPacket.setAddress(host); |
| sendPacket.setPort(port); |
| |
| NtpV3Packet recMessage = new NtpV3Impl(); |
| DatagramPacket receivePacket = recMessage.getDatagramPacket(); |
| |
| /* |
| * Must minimize the time between getting the current time, |
| * timestamping the packet, and sending it out which |
| * introduces an error in the delay time. |
| * No extraneous logging and initializations here !!! |
| */ |
| TimeStamp now = TimeStamp.getCurrentTime(); |
| |
| // Note that if you do not set the transmit time field then originating time |
| // in server response is all 0's which is "Thu Feb 07 01:28:16 EST 2036". |
| message.setTransmitTime(now); |
| |
| _socket_.send(sendPacket); |
| _socket_.receive(receivePacket); |
| |
| long returnTime = System.currentTimeMillis(); |
| // create TimeInfo message container but don't pre-compute the details yet |
| TimeInfo info = new TimeInfo(recMessage, returnTime, false); |
| |
| return info; |
| } |
| |
| /*** |
| * Retrieves the time information from the specified server on the |
| * default NTP port and returns it. The time is the number of miliiseconds |
| * since 00:00 (midnight) 1 January 1900 UTC, as specified by RFC 1305. |
| * This method reads the raw NTP packet and constructs a <i>TimeInfo</i> |
| * object that allows access to all the fields of the NTP message header. |
| * <p> |
| * @param host The address of the server. |
| * @return The time value retrieved from the server. |
| * @exception IOException If an error occurs while retrieving the time. |
| ***/ |
| public TimeInfo getTime(InetAddress host) throws IOException |
| { |
| return getTime(host, NtpV3Packet.NTP_PORT); |
| } |
| |
| /*** |
| * Returns the NTP protocol version number that client sets on request packet |
| * that is sent to remote host (e.g. 3=NTP v3, 4=NTP v4, etc.) |
| * |
| * @return the NTP protocol version number that client sets on request packet. |
| * @see #setVersion(int) |
| ***/ |
| public int getVersion() |
| { |
| return _version; |
| } |
| |
| /*** |
| * Sets the NTP protocol version number that client sets on request packet |
| * communicate with remote host. |
| * |
| * @param version the NTP protocol version number |
| ***/ |
| public void setVersion(int version) |
| { |
| _version = version; |
| } |
| |
| } |