Java tutorial
package org.urbancortex.presenter; /** * Created by Panos on 03/06/2015. */ import org.apache.commons.net.ntp.*; import java.io.IOException; import java.net.InetAddress; import java.net.SocketException; import java.net.UnknownHostException; import java.text.NumberFormat; import java.util.Arrays; import java.util.Timer; import java.util.TimerTask; import static org.urbancortex.presenter.Presenter.remoteIP; /* * 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. */ /*** * This is an example program demonstrating how to use the NTPUDPClient * class. This program sends a Datagram client request packet to a * Network time Protocol (NTP) service port on a specified server, * retrieves the time, and prints it to standard output along with * the fields from the NTP message header (e.g. stratum level, reference id, * poll interval, root delay, mode, ...) * See <A HREF="ftp://ftp.rfc-editor.org/in-notes/rfc868.txt"> the spec </A> * for details. * <p> * Usage: NTPClient <hostname-or-address-list> * <br> * Example: NTPClient clock.psu.edu * * @author Jason Mathews, MITRE Corp ***/ public final class NTPClient { private static final NumberFormat numberFormat = new java.text.DecimalFormat("0.00"); private static boolean socketTimeout; /** * Process <code>TimeInfo</code> object and print its details. * @param info <code>TimeInfo</code> object. */ public static void processResponse(TimeInfo info) { NtpV3Packet message = info.getMessage(); int stratum = message.getStratum(); String refType; if (stratum <= 0) { refType = "(Unspecified or Unavailable)"; } else if (stratum == 1) { refType = "(Primary Reference; e.g., GPS)"; // GPS, radio clock, etc. } else { refType = "(Secondary Reference; e.g. via NTP or SNTP)"; } // stratum should be 0..15... System.out.println(" Stratum: " + stratum + " " + refType); int version = message.getVersion(); int li = message.getLeapIndicator(); System.out.println(" leap=" + li + ", version=" + version + ", precision=" + message.getPrecision()); System.out.println(" mode: " + message.getModeName() + " (" + message.getMode() + ")"); int poll = message.getPoll(); // poll value typically btwn MINPOLL (4) and MAXPOLL (14) System.out.println( " poll: " + (poll <= 0 ? 1 : (int) Math.pow(2, poll)) + " seconds" + " (2 ** " + poll + ")"); double disp = message.getRootDispersionInMillisDouble(); System.out.println(" rootdelay=" + numberFormat.format(message.getRootDelayInMillisDouble()) + ", rootdispersion(ms): " + numberFormat.format(disp)); int refId = message.getReferenceId(); String refAddr = NtpUtils.getHostAddress(refId); String refName = null; if (refId != 0) { if (refAddr.equals("127.127.1.0")) { refName = "LOCAL"; // This is the ref address for the Local Clock } else if (stratum >= 2) { // If reference id has 127.127 prefix then it uses its own reference clock // defined in the form 127.127.clock-type.unit-num (e.g. 127.127.8.0 mode 5 // for GENERIC DCF77 AM; see refclock.htm from the NTP software distribution. if (!refAddr.startsWith("127.127")) { try { InetAddress addr = InetAddress.getByName(refAddr); String name = addr.getHostName(); if (name != null && !name.equals(refAddr)) { refName = name; } } catch (UnknownHostException e) { // some stratum-2 servers sync to ref clock device but fudge stratum level higher... (e.g. 2) // ref not valid host maybe it's a reference clock name? // otherwise just show the ref IP address. refName = NtpUtils.getReferenceClock(message); } } } else if (version >= 3 && (stratum == 0 || stratum == 1)) { refName = NtpUtils.getReferenceClock(message); // refname usually have at least 3 characters (e.g. GPS, WWV, LCL, etc.) } // otherwise give up on naming the beast... } if (refName != null && refName.length() > 1) { refAddr += " (" + refName + ")"; } System.out.println(" Reference Identifier:\t" + refAddr); TimeStamp refNtpTime = message.getReferenceTimeStamp(); System.out.println(" Reference Timestamp:\t" + refNtpTime + " " + refNtpTime.toDateString()); // Originate Time is time request sent by client (t1) TimeStamp origNtpTime = message.getOriginateTimeStamp(); System.out.println(" Originate Timestamp:\t" + origNtpTime + " " + origNtpTime.toDateString()); long destTime = info.getReturnTime(); // Receive Time is time request received by server (t2) TimeStamp rcvNtpTime = message.getReceiveTimeStamp(); System.out.println(" Receive Timestamp:\t" + rcvNtpTime + " " + rcvNtpTime.toDateString()); // Transmit time is time reply sent by server (t3) TimeStamp xmitNtpTime = message.getTransmitTimeStamp(); System.out.println(" Transmit Timestamp:\t" + xmitNtpTime + " " + xmitNtpTime.toDateString()); // Destination time is time reply received by client (t4) TimeStamp destNtpTime = TimeStamp.getNtpTime(destTime); System.out.println(" Destination Timestamp:\t" + destNtpTime + " " + destNtpTime.toDateString()); info.computeDetails(); // compute offset/delay if not already done Long offsetValue = info.getOffset(); Long delayValue = info.getDelay(); String delay = (delayValue == null) ? "N/A" : delayValue.toString(); String offset = (offsetValue == null) ? "N/A" : offsetValue.toString(); System.out.println(" Roundtrip delay(ms)=" + delay + ", clock offset(ms)=" + offset); // offset in ms } public static TimeInfo main(String[] args) { System.out.println(args); if (args.length == 0) { System.err.println("Usage: NTPClient <hostname-or-address-list>"); System.exit(1); } NTPUDPClient client = new NTPUDPClient(); // We want to timeout if a response takes longer than 10 seconds client.setDefaultTimeout(5000); try { client.open(); for (String arg : args) { System.out.println(); try { InetAddress hostAddr = InetAddress.getByName(arg); System.out.println("> " + hostAddr.getHostName() + "/" + hostAddr.getHostAddress()); TimeInfo info = client.getTime(hostAddr); processResponse(info); return info; } catch (IOException ioe) { ioe.printStackTrace(); socketTimeout = true; // csv_logger.stopNTPTask(); System.out.println("couldn't establish a connection" + ioe); } } } catch (SocketException e) { e.printStackTrace(); socketTimeout = true; // csv_logger.stopNTPTask(); System.out.println("couldn't establish a connection" + e); } client.close(); return null; } public static void getTimeOffset() { socketTimeout = false; if (Presenter.remoteIP != null) { System.out.println("getting time offset"); int[] a = new int[10]; int sum = 0; // TimeInfo info = null; for (int i = 0; i < a.length; i++) { TimeInfo info = null; if (remoteIP != null && !socketTimeout) { info = NTPClient.main(new String[] { remoteIP }); //"time-a.nist.gov" } if (info != null) { info.computeDetails(); // compute offset/delay if not already done Long offsetValue = info.getOffset(); Long delayValue = info.getDelay(); String delay = (delayValue == null) ? "N/A" : delayValue.toString(); String offset = (offsetValue == null) ? "N/A" : offsetValue.toString(); Presenter.timeOffset_timestamp = info.getMessage().getReceiveTimeStamp().toDateString() .replaceAll(", ", " "); a[i] = Integer.parseInt(offset); } if (socketTimeout) { break; } System.out.println(i); } for (int i = 0; i < a.length; i++) { sum += a[i]; } Presenter.timeOffset = sum / a.length; Presenter.timeOffset_Array = Arrays.toString(a).replaceAll(", ", ";"); } } }