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/*
*
* 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.
*
*/
package org.apache.qpid.test.framework.clocksynch;
import org.apache.qpid.junit.extensions.ShutdownHookable;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.net.SocketTimeoutException;
import java.nio.ByteBuffer;
/**
* UDPClockReference supplies a refernce clock signal (generated from System.nanoTime()).
*
* <p/><table id="crc"><caption>CRC Card</caption>
* <tr><th> Responsibilities <th> Collaborations
* <tr><td> Supply a reference clock signal.
* </table>
*
* @todo Port hard coded. Make configurable.
*
* @todo Errors rethrown as runtimes, or silently terminate the service. Could add better error handling if needed.
*/
public class UDPClockReference implements Runnable, ShutdownHookable
{
/** Used for debugging. */
// private static final Logger log = Logger.getLogger(UDPClockReference.class);
/** Defines the timeout to use when polling the socket for time requests. */
private static final int TIMEOUT = 200;
/** Defines the port to run the clock reference on. */
public static final int REFERENCE_PORT = 4444;
/** Holds the socket to receive clock reference requests on. */
protected DatagramSocket socket = null;
/** Flag used to indicate that the time server should keep running. Set to false to terminate. */
protected boolean publish = true;
/**
* Creates a clock reference service on the standard port.
*/
public UDPClockReference()
{
try
{
socket = new DatagramSocket(REFERENCE_PORT);
socket.setSoTimeout(TIMEOUT);
}
catch (SocketException e)
{
throw new RuntimeException(e);
}
}
/**
* Implements the run loop for this reference time server. This waits for incoming time requests, and replies to
* any, with a message with the local time stamp in it. Periodically (controlled by {@link #TIMEOUT}), the run
* loop will check if the {@link #publish} flag has been cleared, and terminate the reference time service if so.
*/
public void run()
{
byte[] buf = new byte[256];
ByteBuffer bbuf = ByteBuffer.wrap(buf);
while (publish)
{
try
{
// Wait for a reference time request.
DatagramPacket packet = new DatagramPacket(buf, buf.length);
boolean timedOut = false;
try
{
socket.receive(packet);
}
catch (SocketTimeoutException e)
{
timedOut = true;
}
if (!timedOut)
{
// Work out from the received packet, where to reply to.
InetAddress address = packet.getAddress();
int port = packet.getPort();
// Respond to the time request by sending back the local clock as the reference time.
bbuf.putLong(System.nanoTime());
bbuf.flip();
packet = new DatagramPacket(bbuf.array(), bbuf.capacity(), address, port);
socket.send(packet);
}
}
catch (IOException e)
{
publish = false;
}
}
socket.close();
}
/**
* Supplies a shutdown hook.
*
* @return The shut down hook.
*/
public Thread getShutdownHook()
{
return new Thread(new Runnable()
{
public void run()
{
publish = false;
}
});
}
/**
* For testing purposes. Runs a reference clock on the default port.
*
* @param args None.
*/
public static void main(String[] args)
{
try
{
// Create the clock reference service.
UDPClockReference clock = new UDPClockReference();
// Set up a shutdown hook for it.
Runtime.getRuntime().addShutdownHook(clock.getShutdownHook());
// Start the service.
clock.run();
}
catch (Exception e)
{
e.printStackTrace();
System.exit(1);
}
}
}
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