public class NIOServer {private static final String HOST = "localhost";private static final int PORT = 10086;public static void main(String[] args) {ServerSocketChannel serverSocketChannel = null;ServerSocket serverSocket = null;Selector selector = null;try {serverSocketChannel = ServerSocketChannel.open();//工厂方法创建ServerSocketChannelserverSocket = serverSocketChannel.socket(); //获取channel对应的ServerSocketserverSocket.bind(new InetSocketAddress(HOST, PORT)); //绑定地址serverSocketChannel.configureBlocking(false); //设置ServerSocketChannel非阻塞模式selector = Selector.open();//工厂方法创建SelectorserverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);//通道注册选择器，接受连接就绪状态。while (true) {//循环检查if (selector.select() == 0) {//阻塞检查，当有就绪状态发生，返回键集合continue;}// if (selector.select(2000) == 0) {//     //在等待信道准备的同时，也可以异步地执行其他任务，  这里打印*//     System.out.print("*");//     continue;// }Iterator<SelectionKey> it = selector.selectedKeys().iterator(); //获取就绪键遍历对象。while (it.hasNext()) {SelectionKey selectionKey = it.next();//处理就绪状态if (selectionKey.isAcceptable()) {ServerSocketChannel schannel = (ServerSocketChannel) selectionKey.channel();//只负责监听，阻塞，管理，不发送、接收数据SocketChannel socketChannel = schannel.accept();//就绪后的操作，刚到达的socket句柄if (null == socketChannel) {continue;}socketChannel.configureBlocking(false);socketChannel.register(selector, SelectionKey.OP_READ); //告知选择器关心的通道，准备好读数据} else if (selectionKey.isReadable()) {SocketChannel socketChannel = (SocketChannel) selectionKey.channel();ByteBuffer byteBuffer = ByteBuffer.allocate(4 * 1024);System.out.println(socketChannel.getRemoteAddress());int read = socketChannel.read(byteBuffer);if (read == -1) {//如果不关闭会一直产生isReadable这个消息
                            selectionKey.cancel();socketChannel.close();} else {StringBuilder result = new StringBuilder();while (read > 0) {//确保读完
                                byteBuffer.flip();result.append(new String(byteBuffer.array()));byteBuffer.clear();//每次清空 对应上面flip()read = socketChannel.read(byteBuffer);}System.out.println("server receive: " + result.toString());socketChannel.register(selector, SelectionKey.OP_WRITE);}} else if (selectionKey.isWritable()) {SocketChannel socketChannel = (SocketChannel) selectionKey.channel();String sendStr = "server send data: " + Math.random();ByteBuffer send = ByteBuffer.wrap(sendStr.getBytes());while (send.hasRemaining()) {socketChannel.write(send);}socketChannel.register(selector, SelectionKey.OP_READ);System.out.println(sendStr);}it.remove();}}} catch (IOException e) {e.printStackTrace();}}
}

public class NIOClient {public static void main(String[] args) throws Exception {SocketChannel clntChan = SocketChannel.open();clntChan.configureBlocking(false);if (!clntChan.connect(new InetSocketAddress("localhost", 10086))) {//不断地轮询连接状态，直到完成连接while (!clntChan.finishConnect()) {//在等待连接的时间里，可以执行其他任务，以充分发挥非阻塞IO的异步特性//这里为了演示该方法的使用，只是一直打印"."System.out.print(".");}}//为了与后面打印的"."区别开来，这里输出换行符System.out.print("\n");//分别实例化用来读写的缓冲区ByteBuffer writeBuf = ByteBuffer.wrap("send send send".getBytes());ByteBuffer readBuf = ByteBuffer.allocate("send".getBytes().length - 1);while (writeBuf.hasRemaining()) {//如果用来向通道中写数据的缓冲区中还有剩余的字节，则继续将数据写入信道
            clntChan.write(writeBuf);}Thread.sleep(10000);StringBuffer stringBuffer = new StringBuffer();//如果read（）接收到-1，表明服务端关闭，抛出异常while ((clntChan.read(readBuf)) > 0) {readBuf.flip();stringBuffer.append(new String(readBuf.array(), 0, readBuf.limit()));readBuf.clear();}//打印出接收到的数据System.out.println("Client Received: " + stringBuffer.toString());//关闭信道
        clntChan.close();}
}

public void write(MessageSession session, ByteBuffer buffer) throws ClosedChannelException {SelectionKey key = session.key();if((key.interestOps() & SelectionKey.OP_WRITE) == 0) {key.interestOps(key.interestOps() | SelectionKey.OP_WRITE);}try {writebuf.put(buffer);} catch(Exception e) {System.out.println("want put:"+buffer.remaining()+", left:"+writebuf.remaining());e.printStackTrace();}selector.wakeup();
}

while(true) {selector.select();.....if(key.isWritable()) {MessageSession session = (MessageSession)key.attachment();//System.out.println("Select a write");synchronized(session) {writebuf.flip();SocketChannel channel = (SocketChannel)key.channel();int count = channel.write(writebuf);//System.out.println("write "+count+" bytes");
          writebuf.clear();key.interestOps(SelectionKey.OP_READ);}}......}