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Commons Net example source code file (NTPUDPClient.java)
The Commons Net NTPUDPClient.java source codepackage 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 * and call <a href="#getTime"> getTime to retrieve the time. Then call * <a href="org.apache.commons.net.DatagramSocketClient.html#close"> close * to close the connection properly. * Successive calls to <a href="#getTime"> getTime 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: 489397 $ $Date: 2006-12-21 16:28:51 +0000 (Thu, 21 Dec 2006) $ ***/ 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 * 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 * 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; } } Other Commons Net examples (source code examples)Here is a short list of links related to this Commons Net NTPUDPClient.java source code file: |
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