/////////////////////////////////// SERVER ///////////////////////
import java.util.Map;
import java.util.HashMap;
import java.util.Date;
import java.util.Iterator;

import java.nio.channels.ServerSocketChannel;
import java.nio.channels.Selector;
import java.nio.channels.SelectionKey;
import java.nio.channels.SocketChannel;

import java.io.IOException;

import java.net.ServerSocket;
import java.net.Socket;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.BindException;

import java.lang.SecurityException;

public class Server
	implements Runnable
{	
	ServerSocketChannel serverSocketChannel;
	ServerSocket serverSocket;
	Dispatcher dispatcher;
	
	boolean running;
	
    public Server()
    {
		dispatcher = new Dispatcher();
		new Thread(this).start();
    }

    public void run()
    {
		try
		{
			serverSocketChannel = ServerSocketChannel.open();
			serverSocketChannel.configureBlocking(true);			
			
			serverSocket = serverSocketChannel.socket();
			serverSocket.bind(new InetSocketAddress(17223));
			
		}
		catch(BindException e1)
		{
			System.out.println("Puerto " + 17223 + " ocupado");
			return;
		}
		catch(SecurityException e2)
		{
			System.out.println("Permisos");
			return;
		}
		catch(IOException e3)
		{
			System.out.println("Imposible iniciar servidor");
			
			if(serverSocket != null)
			{
				try
				{
					serverSocket.close();
				}
				catch(IOException e4){}
			}
			return;
		}
		
		System.out.println("Servidor iniciado, escuchando en puerto : 17223");
		
		running = true;
		
		while(running)
		{
			SocketChannel socketChannel = null;
			try
			{
				socketChannel = serverSocketChannel.accept();				
				socketChannel.configureBlocking(false);
			}
			catch(IOException ioe)
			{
				System.out.println("No se obtuvo un nuevo socketChannel");
				continue;
			}
			
			InetAddress addr = socketChannel.socket().getInetAddress();
			System.out.println("Conexion recibida desde (" 
				+ addr.getHostAddress() + ") : " + addr.getHostName());
			
			//se registra el nuevo cliente en el siguiente dispatcher
			dispatcher.register(socketChannel);
			
		}
		
		System.out.println("Servidor detenido");
    }
	
    public void stop()
    {
		try
        {
			running = false;
            serverSocket.close();
        }
        catch(IOException e )
        {
            System.out.println("Cerrar serverSocket");
        }
    } 
		
	public static void main(String[] args)
	{		
		try
		{
			Server server = new Server();
				
			//se iguala a nul algunos parametros para que el Garbage Collector
			//los libere, ya que son variables que nunca se volverán a ocupar
		}
		catch(Exception e)
		{
			System.out.println("Excepcion ocurrida en el Main");
			System.exit(0);
		}
	}	
}



import java.nio.channels.Selector;
import java.nio.channels.SelectionKey;
import java.nio.channels.SocketChannel;
import java.nio.ByteBuffer;

import java.io.IOException;

import java.util.Iterator;

import java.lang.Thread;

public class Dispatcher
	extends Thread
{
	
	Object guard = new Object();
	Selector selector;
	boolean running;
	
	public Dispatcher()
	{
		try
		{
			this.selector = Selector.open();
			this.running = true;
			start();
		}
		catch(IOException e)
		{
			System.out.println("Selector open failed");
		}
	}
	
	public void register(SocketChannel socketChannel)
	{
		synchronized(guard)
		{			
			selector.wakeup();
			try
			{
				socketChannel.register(selector, SelectionKey.OP_READ);
			}
			catch(Exception e)
			{
				System.out.println("Channel registration failed");
			}			
		}
	}
	
	public void run()
	{
		running = true;
		while(running) 
		{
			synchronized(guard) 
			{ 
				// detener el thread del dispatcher si alguien mas esta 
				// accesando al selector (register() method)
			}
			
			try
			{
				//Si regresa 0, no hay operaciones de E/S
				int n = selector.select();
				System.out.println("n : " + n);
				if(n < 1) continue;
			}
			catch(IOException e)
			{
				System.out.println("selector.select() Error");
				continue;
			}
			
			//Un cliente solo puede generar eventos de lectura, es decir, 
			//escritura para el y lectura para el server
			Iterator<SelectionKey> it = selector.selectedKeys().iterator();
			while(it.hasNext()) 
			{
				SelectionKey key = it.next(); 
				it.remove();
								
				if(key.isValid() && key.isReadable()) 
				{
					// se registra la peticion en la cola de peticiones
					System.out.println("read event valid and readable");
				}
			}
		}
	}

	public void killIt()
	{
		running = false;
	}
}




////////////////////////////  CLIENT ////////////////////////////////
import java.nio.channels.SocketChannel;
import java.nio.channels.Channels;
import java.nio.channels.WritableByteChannel;

import java.nio.ByteBuffer;

import java.net.InetSocketAddress;
import java.net.Socket;

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Connection 
{

    public static void main(String[] args) 
	{
		try
		{
			SocketChannel sc = SocketChannel.open();
			
			System.out.println("making conection ...");
			sc.socket().connect(new InetSocketAddress("localhost", 17223));
			Thread.currentThread().sleep(3000);			
			//Socket socket = new Socket("localhost", 17223);
			System.out.println("connection established");
			
			BufferedReader in = new BufferedReader(
				new InputStreamReader( System.in ) );
				
			//WritableByteChannel output = Channels.newChannel(System.out);
			ByteBuffer buffer = ByteBuffer.allocate(100);
			String cad = in.readLine();
			
			while(!"exit".equals(cad.toLowerCase()))
			{
				buffer.put(cad.getBytes());
				buffer.flip();
				sc.write(buffer);
				
				buffer.clear();
				cad = in.readLine();
			}
			//Thread.currentThread().sleep(3000);
			sc.close();
			sc.socket().close();			
			//Thread.currentThread().sleep(5000);
			//socket.close();
		}
		catch(Exception e)
		{			
			e.printStackTrace();
			System.exit(0);
		}
    }
}