/*
* Copyright (c) 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017 David Berkman
*
* This file is part of the SmallMind Code Project.
*
* The SmallMind Code Project is free software, you can redistribute
* it and/or modify it under either, at your discretion...
*
* 1) The terms of GNU Affero General Public License as published by the
* Free Software Foundation, either version 3 of the License, or (at
* your option) any later version.
*
* ...or...
*
* 2) The terms of the Apache License, Version 2.0.
*
* The SmallMind Code Project is distributed in the hope that it will
* be useful, but WITHOUT ANY WARRANTY; without even the implied warranty
* of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License or Apache License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* and the Apache License along with the SmallMind Code Project. If not, see
* <http://www.gnu.org/licenses/> or <http://www.apache.org/licenses/LICENSE-2.0>.
*
* Additional permission under the GNU Affero GPL version 3 section 7
* ------------------------------------------------------------------
* If you modify this Program, or any covered work, by linking or
* combining it with other code, such other code is not for that reason
* alone subject to any of the requirements of the GNU Affero GPL
* version 3.
*/
package org.smallmind.nutsnbolts.ntp;
import java.io.IOException;
import java.net.InetAddress;
import java.security.SecureRandom;
import org.apache.commons.net.ntp.NTPUDPClient;
import org.apache.commons.net.ntp.TimeInfo;
public final class NTPTime {
private static final SecureRandom RANDOM = new SecureRandom();
private final String[] hostNames;
public NTPTime (String[] hostNames) {
if ((hostNames == null) || (hostNames.length == 0)) {
throw new IllegalArgumentException("No host names provided");
}
this.hostNames = hostNames;
}
public final long getOffset (int timeoutMillis)
throws IOException {
NTPUDPClient client = new NTPUDPClient();
client.setDefaultTimeout(timeoutMillis);
client.open();
try {
TimeInfo timeInfo;
timeInfo = client.getTime(InetAddress.getByName(hostNames[RANDOM.nextInt(hostNames.length)]));
timeInfo.computeDetails();
return timeInfo.getOffset();
}
finally {
client.close();
}
}
}