Android Open Source - Soutils Beacon Sender And Receiver

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License

The source code is released under:

MIT License

Java Source Code

/* The MIT License (MIT)
//w w w. j  ava 2 s  . c o m
Copyright (c) 2012 Jerome Wagener

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
the Software, and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.*/

package com.jeromewagener.soutils.beaconing;

import java.io.InterruptedIOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;

import com.jeromewagener.soutils.Parameters;
import com.jeromewagener.soutils.messaging.MessageType;
import com.jeromewagener.soutils.messaging.SoutilsMessage;
import com.jeromewagener.soutils.messaging.SoutilsObservable;
import com.jeromewagener.soutils.messaging.SoutilsObserver;

/** A SoutilsObservable thread which listens for UDP beacons which are then 
 * forwarded to to all registered SoutilsObservers. Opposed to the BeaconReceiver,
 * this thread allows to simultaneously send UDP beacons using the same port */
public class BeaconSenderAndReceiver extends SoutilsObservable  {
  private static final String UTF_8 = "UTF-8";
  /** The port used to send and receive beacon messages at the same time */
  private final int port;
  /** The message to be transferred by the beacon */
  private String message;
  /** This variable must be set to true in order to stop the thread */
  private boolean done = false;
  /** The broadcast address to be used for distributing the beacon */
  private InetAddress broadcastAddress;

  /** Creates a new thread which is able to sent and receive UDP beacons at the same time. As for any Java thread
   * the {@link #start()} method must be called to start the thread. The received beacons are forwarded to the registered
   * SoutilsObserver. More observers can be added using the register method.
   * @param port the port used to send and receive beacon messages at the same time
   * @param message the beacon message to be broadcasted
   * @param broadcastAddress the IP broadcast address to be used
   * @param soutilsObserver the observer to be notified in case of received beacons
   * @see SoutilsObserver
   * @see #start()
   */
  public BeaconSenderAndReceiver(String beaconMessage, InetAddress broadcastAddress, int port, SoutilsObserver soutilsObserver) {
    this.port = port;
    this.broadcastAddress = broadcastAddress;
    this.message = beaconMessage;
    this.registerSoutilsObserver(soutilsObserver);
  }

  /** Replace the beacon message by another beacon message. */
  public void updateBeacon(String message) {
    this.message = message;
  }
  
  /** Call this method to stop the thread and to prevent it from receiving or sending any further beacons.
   * Once the thread has been stopped, it cannot be started again. You must instead instantiate a new BeaconSenderAndReceiver instead.
   * @see #start() */
  public void done() {
    done = true;
  }

  /** This method sends out a single beacon with the message specified within the constructor */
  private void broadcast(DatagramSocket socket) {
    try {
      DatagramPacket packet = new DatagramPacket(
          message.getBytes(), message.length(), broadcastAddress, port);
      socket.send(packet);
    } catch (Exception exception) {
      notifyAllObservers(new SoutilsMessage(MessageType.ERROR, SoutilsMessage.INTERNAL, exception));
    }
  }

  /** Starts the BeaconSenderAndReceiver thread which will continuously send out beacons with the message specified
   * within the constructor. At the same time, the thread will listen to incoming beacons on the same port. This
   * includes beacons sent by the local host.
   * @see BeaconParameters 
   * @see #done() */
  @Override
  public void run() {
    DatagramSocket datagramSocket = null;

    try {
      datagramSocket = new DatagramSocket(port);
      datagramSocket.setBroadcast(true);
      datagramSocket.setSoTimeout(Parameters.BEACON_MILLISECONDS_UNTIL_DATAGRAM_SOCKET_TIMEOUT);
    } catch (SocketException socketException) {
      notifyAllObservers(new SoutilsMessage(MessageType.ERROR, SoutilsMessage.INTERNAL, socketException));
      datagramSocket.close();
      return;
    }

    while (!done) {
      try {
        broadcast(datagramSocket);        

        byte[] datagramBuffer = new byte[Parameters.BEACON_DATAGRAM_BUFFER_SIZE];
        DatagramPacket packet = new DatagramPacket(datagramBuffer, datagramBuffer.length);
        datagramSocket.receive(packet);
        notifyAllObservers(new SoutilsMessage(
            MessageType.BEACON, packet.getAddress().getHostAddress(), new String(packet.getData(), UTF_8).trim()));

        Thread.sleep(Parameters.BEACON_MILLISECONDS_UNTIL_NEXT_BROADCAST);
      } catch (InterruptedIOException iie) {
        // The socket timed-out, re-enter the loop and listen again      
        continue;
      } catch(Exception exception) {
        notifyAllObservers(new SoutilsMessage(MessageType.ERROR, SoutilsMessage.INTERNAL, exception));
        datagramSocket.close();
        return;
      }
    }

    datagramSocket.close();
  }
}

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