import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Iterator;public class NIOServer {private Selector selector;public void initServer(int port) throws IOException {ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();// 打开服务器套接字通道serverSocketChannel.configureBlocking(false);// 设置为非阻塞模式serverSocketChannel.socket().bind(new InetSocketAddress(port));// 绑定端口this.selector = Selector.open();// 打开选择器// 注册事件，当事件到达，selector。select()会返回，如果没有事件会一直阻塞serverSocketChannel.register(this.selector, SelectionKey.OP_ACCEPT);// 注册选择器，接受客户端连接}public void listen() throws IOException {System.out.println("服务器启动!开始轮询监听消息");while (true) {int ready = this.selector.select();if (ready == 0) {continue;}Iterator items = this.selector.selectedKeys().iterator();while (items.hasNext()) {SelectionKey key = (SelectionKey) items.next();// 删除已经选择的key，防止重复处理items.remove();// 请求连接if (key.isAcceptable()) {ServerSocketChannel serverSocketChannel = (ServerSocketChannel) key.channel();if (serverSocketChannel == null) {continue;}SocketChannel socketChannel = serverSocketChannel.accept();//每次接受新的连接请求会产生新的通道，socketChannel.configureBlocking(false);socketChannel.write(ByteBuffer.wrap(new String("你好，客户端，连接已建立，可以开始通信!").getBytes()));//连接成功，发消息给客户端System.out.println("连接已经建立");socketChannel.register(this.selector, SelectionKey.OP_READ);//准备好接收数据} else if (key.isReadable()) {this.read(key);}}}}public void read(SelectionKey key) throws IOException {SocketChannel socketChannel = (SocketChannel) key.channel();ByteBuffer byteBuffer = ByteBuffer.allocate(100);socketChannel.read(byteBuffer);byte[] data = byteBuffer.array();String msg = new String(data).trim();if (msg.equals("close~!@#$%")) {//收到关闭指令，发送确认关闭的指令给客户端，结束自身通道ByteBuffer sendBuffer = ByteBuffer.wrap(new String("bye close").getBytes());while (sendBuffer.hasRemaining()) {socketChannel.write(sendBuffer);}socketChannel.close();System.out.println("已经关闭");} else {System.out.println("server Receive:" + msg);//服务器收到任何消息都会给客户端发送"收到"socketChannel.write(ByteBuffer.wrap(new String("收到!").getBytes()));}}public static void main(String[] args) {NIOServer server = new NIOServer();try {server.initServer(1377);server.listen();} catch (IOException e) {e.printStackTrace();}}
}

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.util.Iterator;public class NIOClient {private Selector selector;//初始化public void initClient(String ipAddress, int port) throws IOException {SocketChannel socketChannel = SocketChannel.open();//打开套接字通道socketChannel.configureBlocking(false);//非阻塞this.selector = Selector.open();//打开选择器socketChannel.connect(new InetSocketAddress(ipAddress, port));//指定ip地址和端口号用于连接socketChannel.register(this.selector, SelectionKey.OP_CONNECT);//通道注册到选择器中,用于连接}//监听public void listen() throws IOException {while (true) {//当客户端关闭的时候需要结束轮循的动作，这样程序才会结束if (!this.selector.isOpen()) {return;}int ready = this.selector.select();//这个才是真正的轮循啦，得到通道if (ready == 0) {continue;//如果selector中没有SocketChannel,直接开始下一次咯 }Iterator items = this.selector.selectedKeys().iterator();while (items.hasNext()) {SelectionKey key = (SelectionKey) items.next();items.remove();//防止重复处理if (key.isConnectable()) {//连接System.out.println("正在连接，连接成功后，服务器会返回结果!");SocketChannel socketChannel = (SocketChannel) key.channel();// 如果正在连接，则完成连接if (socketChannel.isConnectionPending()) {socketChannel.finishConnect();}socketChannel.register(this.selector, SelectionKey.OP_READ);//重新注册该通道，用于读取数据} else if (key.isReadable()) {//读取this.read(key);}}}}/****************************************************//** 客户端关闭思路* 客户端                            服务器* * 用户输入bye，需要关闭客户端* * "close~!@#$%"   ->           "close~!@#$%"                               约定好的内容("close~!@#$%")*                    * "bye close" <-               "bye close"     ----->服务器通道关闭                      约定好的内容("bye close")* * 客户端通道关闭                    服务器还可以接受别的请求* */public void read(SelectionKey key) throws IOException {SocketChannel socketChannel = (SocketChannel) key.channel();ByteBuffer receiveBuffer = ByteBuffer.allocate(100);socketChannel.read(receiveBuffer);byte[] data = receiveBuffer.array();String msg = new String(data).trim();if (msg.equals("bye close")) {//客户端和服务器约定关闭，收到服务器响应后可以关闭System.out.println("关闭");socketChannel.close();this.selector.close();return;}System.out.println("client receive:" + msg);BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));String readMsg = reader.readLine();ByteBuffer sendBuffer = ByteBuffer.allocate(256);sendBuffer.clear();if(readMsg.equals("bye")){//告诉服务器，准备要撤退，当服务器返回bye close，关闭通道和选择器System.out.println("准备关闭");sendBuffer.put("close~!@#$%".getBytes());sendBuffer.flip();}else{sendBuffer.put(readMsg.getBytes());sendBuffer.flip();}while (sendBuffer.hasRemaining()) {socketChannel.write(sendBuffer);}}public static void main(String[] args) {NIOClient client = new NIOClient();try {client.initClient("127.0.0.1", 1377);client.listen();} catch (IOException e) {e.printStackTrace();}}
}