udpreceiver.java

来自「google公司的用Java写的一个聊天软件的原代码」· Java 代码 · 共 158 行

/***************************************************************************
 *   Copyright 2006-2008 by Christian Ihle                                 *
 *   [e-mail]                                                  *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program 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 for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/

package net.usikkert.kouchat.net;

import java.io.IOException;

import java.net.DatagramPacket;
import java.net.DatagramSocket;

import java.util.logging.Level;
import java.util.logging.Logger;

import net.usikkert.kouchat.Constants;
import net.usikkert.kouchat.event.ReceiverListener;
import net.usikkert.kouchat.misc.ErrorHandler;
import net.usikkert.kouchat.misc.Settings;

/**
 * Receives UDP packets sent directly to the IP address
 * of this machine.
 *
 * @author Christian Ihle
 */
public class UDPReceiver implements Runnable
{
	private static final Logger LOG = Logger.getLogger( UDPReceiver.class.getName() );

	private DatagramSocket udpSocket;
	private ReceiverListener listener;
	private boolean run;
	private Thread worker;
	private final ErrorHandler errorHandler;

	/**
	 * Default constructor.
	 */
	public UDPReceiver()
	{
		errorHandler = ErrorHandler.getErrorHandler();
	}

	/**
	 * The run() method of this thread. Checks for new packets,
	 * extracts the message and IP address, and notifies the listener.
	 */
	public void run()
	{
		while ( run )
		{
			try
			{
				DatagramPacket packet = new DatagramPacket(
						new byte[Constants.NETWORK_PACKET_SIZE], Constants.NETWORK_PACKET_SIZE );

				udpSocket.receive( packet );
				String ip = packet.getAddress().getHostAddress();
				String message = new String( packet.getData(), Constants.MESSAGE_CHARSET ).trim();

				if ( listener != null )
					listener.messageArrived( message, ip );
			}

			catch ( final IOException e )
			{
				LOG.log( Level.WARNING, e.toString() );
			}
		}
	}

	/**
	 * Creates a new UDP socket, and starts a thread listening
	 * on the UDP port. If the UDP port is in use, a new port will be
	 * tried instead.
	 */
	public void startReceiver()
	{
		int port = Constants.NETWORK_PRIVCHAT_PORT;
		int counter = 0;
		boolean done = false;

		while ( counter < 10 && !done )
		{
			try
			{
				udpSocket = new DatagramSocket( port );
				run = true;
				worker = new Thread( this, "UDPReceiverWorker" );
				worker.start();
				done = true;
				Settings.getSettings().getMe().setPrivateChatPort( port );
			}

			catch ( final IOException e )
			{
				LOG.log( Level.SEVERE, e.toString() + " " + port );

				counter++;
				port++;
				Settings.getSettings().getMe().setPrivateChatPort( 0 );
			}
		}

		if ( !done )
		{
			String error = "Failed to initialize udp network:"
					+ "\nNo available listening port between " + Constants.NETWORK_PRIVCHAT_PORT
					+ " and " + ( port - 1 ) + "."
					+ "\n\nYou will not be able to receive private messages!";

			LOG.log( Level.SEVERE, error );
			errorHandler.showError( error );
		}
	}

	/**
	 * Closes the UDP socket, and stops the thread.
	 */
	public void stopReceiver()
	{
		run = false;

		if ( udpSocket != null && !udpSocket.isClosed() )
		{
			udpSocket.close();
		}
	}

	/**
	 * Sets the listener who will receive all the messages
	 * from the UDP packets.
	 *
	 * @param listener The object to register as a listener.
	 */
	public void registerReceiverListener( final ReceiverListener listener )
	{
		this.listener = listener;
	}
}