import java.io.*;
import java.nio.*;
import java.nio.channels.*;
import java.net.*;
import java.util.*;
import java.nio.charset.*;
import java.lang.*;

public class NonBlockingServer
{
    public Selector sel = null;
    public ServerSocketChannel server = null;
    public SocketChannel socket = null;
    public int port = 4900;
    String result = null;

    public NonBlockingServer()
    {
        System.out.println("Inside default ctor");
    }

    public NonBlockingServer(int port)
    {
        System.out.println("Inside the other ctor");
        port = port;
    }

    public void initializeOperations() throws IOException,UnknownHostException
    {
        System.out.println("Inside initialization");
        sel = Selector.open();
        server = ServerSocketChannel.open();
        server.configureBlocking(false);
        InetAddress ia = InetAddress.getLocalHost();
        InetSocketAddress isa = new InetSocketAddress(ia,port);
        server.socket().bind(isa);
    }

    public void startServer() throws IOException
    {
        System.out.println("Inside startserver");
        initializeOperations();
        System.out.println("Abt to block on select()");
        SelectionKey acceptKey = server.register(sel, SelectionKey.OP_ACCEPT ); 

        while (acceptKey.selector().select() > 0 )
        {   

            Set readyKeys = sel.selectedKeys();
            Iterator it = readyKeys.iterator();

            while (it.hasNext()) {
                SelectionKey key = (SelectionKey)it.next();
                it.remove();

                if (key.isAcceptable()) {
                    System.out.println("Key is Acceptable");
                    ServerSocketChannel ssc = (ServerSocketChannel) key.channel();
                    socket = (SocketChannel) ssc.accept();
                    socket.configureBlocking(false);
                    SelectionKey another = socket.register(sel,SelectionKey.OP_READ|SelectionKey.OP_WRITE);
                }
                if (key.isReadable()) {
                    System.out.println("Key is readable");
                    String ret = readMessage(key);
                    if (ret.length() > 0) {
                        writeMessage(socket,ret);
                    }
                }
                if (key.isWritable()) {
                    //System.out.println("The key is writable");
                    String ret = readMessage(key);
                    socket = (SocketChannel)key.channel();
                    if (result.length() > 0 ) {
                        writeMessage(socket,ret);
                    }
                }
            }
        }
    }

    public void writeMessage(SocketChannel socket,String ret)
    {
        System.out.println("Inside the loop");

        if (ret.equals("quit") || ret.equals("shutdown")) {
            return;
        }
        File file = new File(ret);
        try
        {

            RandomAccessFile rdm = new RandomAccessFile(file,"r");
            FileChannel fc = rdm.getChannel();
            ByteBuffer buffer = ByteBuffer.allocate(1024);
            fc.read(buffer);
            buffer.flip();

            Charset set = Charset.forName("us-ascii");
            CharsetDecoder dec = set.newDecoder();
            CharBuffer charBuf = dec.decode(buffer);
            System.out.println(charBuf.toString());
            buffer = ByteBuffer.wrap((charBuf.toString()).getBytes());
            int nBytes = socket.write(buffer);
            System.out.println("nBytes = "+nBytes);
                result = null;
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }

    }

    public String readMessage(SelectionKey key)
    {
        int nBytes = 0;
        socket = (SocketChannel)key.channel();
        ByteBuffer buf = ByteBuffer.allocate(1024);
        try
        {
            nBytes = socket.read(buf);
            buf.flip();
            Charset charset = Charset.forName("us-ascii");
            CharsetDecoder decoder = charset.newDecoder();
            CharBuffer charBuffer = decoder.decode(buf);
            result = charBuffer.toString();

        }
        catch(IOException e)
        {
            e.printStackTrace();
        }
        return result;
    }

    public static void main(String args[])
    {
        NonBlockingServer nb = new NonBlockingServer();
        try
        {
            nb.startServer();
        }
        catch (IOException e)
        {
            e.printStackTrace();
            System.exit(-1);
        }

    }
}

import java.nio.*;
import java.nio.channels.*;
import java.net.*;
import java.io.*;
import java.nio.channels.spi.*;
import java.nio.charset.*;
import java.lang.*;

public class Client
{
    public SocketChannel client = null;
    public InetSocketAddress isa = null;
    public RecvThread rt = null;

    public Client()
    {
    }

    public void makeConnection()
    {
        int result = 0;
        try
        {

            client = SocketChannel.open();
                isa = new InetSocketAddress("liudong",4900);
            client.connect(isa);
            client.configureBlocking(false);
            receiveMessage();    
        }
        catch(UnknownHostException e)
        {
            e.printStackTrace();
        }
        catch(IOException e)
        {
            e.printStackTrace();
        }
        while ((result = sendMessage()) != -1)
        {
        }

        try
        {
            client.close();
            System.exit(0);
        }
        catch(IOException e)
        {
            e.printStackTrace();
        }
    }

    public int sendMessage()
    {
        System.out.println("Inside SendMessage");
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        String msg = null;
        ByteBuffer bytebuf = ByteBuffer.allocate(1024);
        int nBytes = 0;
        try
        {
            msg = in.readLine();
            System.out.println("msg is "+msg);
            bytebuf = ByteBuffer.wrap(msg.getBytes());
            nBytes = client.write(bytebuf);
            System.out.println("nBytes is "+nBytes);
            if (msg.equals("quit") || msg.equals("shutdown")) {
                System.out.println("time to stop the client");
                interruptThread();
                try
                {
                    Thread.sleep(5000);
                }
                catch(Exception e)
                {
                    e.printStackTrace();
                }
                client.close();
                return -1;
            }

        }
        catch(IOException e)
        {
            e.printStackTrace();
        }
        System.out.println("Wrote "+nBytes +" bytes to the server");
        return nBytes;
    }

    public void receiveMessage()
    {
        rt = new RecvThread("Receive THread",client);
        rt.start();

    }

    public void interruptThread()
    {
        rt.val = false;
    }

    public static void main(String args[])
    {
        Client cl = new Client();
        cl.makeConnection();
    }

    public class RecvThread extends Thread
    {
        public SocketChannel sc = null;
        public boolean val = true;

        public RecvThread(String str,SocketChannel client)
        {
            super(str);
            sc = client;
        }

        public void run() {

            System.out.println("Inside receivemsg");
            int nBytes = 0;
            ByteBuffer buf = ByteBuffer.allocate(2048);
            try
            {
                while (val)
                {
                    while ( (nBytes = nBytes = client.read(buf)) > 0){
                        buf.flip();
                        Charset charset = Charset.forName("us-ascii");
                        CharsetDecoder decoder = charset.newDecoder();
                        CharBuffer charBuffer = decoder.decode(buf);
                        String result = charBuffer.toString();
                                    System.out.println(result);
                        buf.flip();

                    }
                }

            }
            catch(IOException e)
            {
                e.printStackTrace();

            }

        }
    }
}