服务端代码:

public static void main(String[] args) throws Exception 
	{
		// 创建选择器  
		Selector selector = Selector.open();
		// 打开监听信道  
		ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
		// 与本地端口绑定  
		serverSocketChannel.socket().bind(new InetSocketAddress(9999));
		// 设置为非阻塞模式 
		serverSocketChannel.configureBlocking(false); 
		// 将选择器绑定到监听信道,只有非阻塞信道才可以注册选择器.并在注册过程中指出该信道可以进行Accept操作  
		serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
		
		while (true) 
		{
			// 等待某信道就绪
			int selectInt = selector.select();
			if (selectInt == 0)
				continue;
			// 取得迭代器.selectedKeys()中包含了每个准备好某一I/O操作的信道的SelectionKey
			Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
			while (iterator.hasNext())
			{
				SelectionKey selectionKey = iterator.next();
				// 有客户端连接请求时 
				if (selectionKey.isAcceptable())
					handleAccept(selectionKey);
				// 从客户端读取数据  
				if (selectionKey.isReadable())
					handleRead(selectionKey);
				// 向客户端发送数据
			    if (selectionKey.isWritable())
					handleWrite(selectionKey);
				iterator.remove();
			}
		}
	}
	
	
	public static void handleAccept(SelectionKey selectionKey) throws Exception
	{
		// 返回创建此键的通道，接受客户端建立连接的请求，并返回 SocketChannel 对象
		ServerSocketChannel ServerSocketChannel = (ServerSocketChannel)selectionKey.channel();
		SocketChannel clientChannel = ServerSocketChannel.accept();
		// 非阻塞式 
		clientChannel.configureBlocking(false);
		// 注册到selector
		clientChannel.register(selectionKey.selector(), SelectionKey.OP_READ);
		
		sendInfo(clientChannel, "连接服务器成功!");
		System.err.println("client IP :" + clientChannel.socket().getRemoteSocketAddress());
	}
	
	public static void handleRead(SelectionKey key) throws Exception
	{
		SocketChannel channel = (SocketChannel) key.channel();
		String msg = "";
		ByteBuffer buffer = ByteBuffer.allocate(1024);
		while(channel.read(buffer) > 0)
		{
			buffer.flip();
			while(buffer.hasRemaining())
				msg += new String(buffer.get(new byte[buffer.limit()]).array());
			buffer.clear();
		}  
		
        System.err.println("收到客户端消息:"+msg);
        
        sendInfo(channel, "服务端消息test!");
	}
	
	public static void handleWrite(SelectionKey key)
	{
		System.out.println("服务端发送信息!");
	}
	
	public static void sendInfo(SocketChannel clientChannel, String msg) throws Exception
	{
		// 向客户端发送连接成功信息
		clientChannel.write(ByteBuffer.wrap(msg.getBytes()));
	}

客户端代码:

	public static void main(String[] args) throws Exception 
	{
		// 创建选择器  
		Selector selector = Selector.open();
		SocketChannel socketChannel = SocketChannel.open();
		socketChannel.configureBlocking(false);
		socketChannel.connect(new InetSocketAddress("localhost", 9999));
		socketChannel.register(selector, SelectionKey.OP_CONNECT); 
		
		while (true) 
		{
			int selectInt = selector.select();
			if (selectInt == 0)
				continue;
			Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
			while(iterator.hasNext())
			{
				SelectionKey key = iterator.next();
				if (key.isConnectable())
					handleConnect(key);
				if (key.isReadable())
					handleRead(key);
				if (key.isWritable())
					handleWrite(key);
				iterator.remove();
			}
		}
		
	}
	
	public static void handleConnect(SelectionKey key) throws Exception
	{
		SocketChannel channel = (SocketChannel) key.channel();
		if (channel.isConnectionPending())
			channel.finishConnect();
		channel.configureBlocking(false);
		channel.register(key.selector(), SelectionKey.OP_READ);
		
		sendInfo(channel, "客户端测试!");
	}
	
	public static void handleRead(SelectionKey key) throws Exception
	{
		SocketChannel channel = (SocketChannel) key.channel();
		String msg = "";
		ByteBuffer buffer = ByteBuffer.allocate(1024);
		while(channel.read(buffer) > 0)
		{
			buffer.flip();
			while(buffer.hasRemaining())
				msg += new String(buffer.get(new byte[buffer.limit()]).array());
			buffer.clear();
		}   
		
        System.err.println("收到服务端消息:"+msg);
	}
	
	public static void handleWrite(SelectionKey key) throws Exception
	{
		System.err.println("客户端写数据!");
	}
	
	public static void sendInfo(SocketChannel clientChannel, String msg) throws Exception
	{
		// 向客户端发送连接成功信息
		clientChannel.write(ByteBuffer.wrap(msg.getBytes()));
	}

参考地址:http://www.iteye.com/magazines/132-Java-NIO

SocketChannel