java nio echo 服务

import java.io.*;
import java.net.*;
import java.nio.*;
import java.nio.channels.*;

public class client
{
        public static void main(String args[]) throws Exception
        {
                SocketChannel channel = SocketChannel.open();
                channel.socket().connect(new InetSocketAddress("127.0.0.1", 8888));

                ByteBuffer buf = ByteBuffer.allocate(20);


                buf.clear();
                buf.put((byte)'a');
                buf.put((byte)'b');
                buf.put((byte)'c');

                buf.flip();
                int written = channel.write(buf);


                buf.clear();
                int len = channel.read(buf);
                buf.flip();
                for (int i = 0; i < len; i++)
                        System.out.print((char)buf.get(i));
                System.out.println("");

                channel.close();

        }
}




import java.io.*;
import java.nio.*;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.net.*;
import java.util.Iterator;

public class ServerNio
{
        static Selector selector;

        public static void handle(SelectionKey key) throws Exception
        {
                if (key.isAcceptable())
                {
                        ServerSocketChannel channel = (ServerSocketChannel) key.channel();

                        SocketChannel socket = channel.accept();

                        socket.configureBlocking(false);
                        socket.register(selector, SelectionKey.OP_READ);
                }

                if (key.isReadable())
                {
                        SocketChannel socket = (SocketChannel) key.channel();

                        ByteBuffer buf = ByteBuffer.allocate(1024);
                        int len;

                        try
                        {

                                buf.clear();
                                if ((len = socket.read(buf)) <= 0)
                                {
                                        socket.close();
                                        key.cancel();
                                        return;
                                }

                                buf.flip();
                                socket.write(buf);
                        }
                        catch(Exception e)
                        {
                                e.printStackTrace();
                        }
                }
        }

        public static void main(String[] args) throws Exception
        {
                selector = Selector.open();

                ServerSocketChannel server = ServerSocketChannel.open();
                server.configureBlocking(false);
                server.socket().bind(new InetSocketAddress(8888));
                server.register(selector, SelectionKey.OP_ACCEPT);

                while (true)
                {
                        selector.select();

                        Iterator<SelectionKey> keyIterator = selector.selectedKeys().iterator();

                        while (keyIterator.hasNext())
                        {
                                SelectionKey key = keyIterator.next();

                                if (key.isValid())
                                {
                                        handle(key);
                                }

                                keyIterator.remove();
                        }
                }
        }
}