服务端:

package com.net.scday3;

import java.io.IOException;

import java.net.InetSocketAddress;

import java.nio.ByteBuffer;

import java.nio.channels.Channel;

import java.nio.channels.SelectionKey;

import java.nio.channels.Selector;

import java.nio.channels.ServerSocketChannel;

import java.nio.channels.SocketChannel;

import java.nio.charset.Charset;

public class NServer {

	//用于检测所有Channel的Selector

	private Selector selector =null;

	//编写实现编码解码的字符集对象

	private Charset charset=Charset.forName("UTF-8");

	public void init() throws IOException{

			selector=Selector.open();

			//通过open方法打开一个未绑定的ServerSocketChannel实例

			ServerSocketChannel server=ServerSocketChannel.open();

			InetSocketAddress isa=new InetSocketAddress("127.0.0.1",30000);

			//将该ServerSocketChannel绑定到指定的IP地址

			server.socket().bind(isa);

			//设置ServerSocket以非阻塞方式工作

			server.configureBlocking(false);

			//将Server注册到Selector对象

		    server.register(selector, SelectionKey.OP_ACCEPT);

            while(selector.select()>0){

            	//依次处理selector上的每个已选择的SelectionKey

            	for(SelectionKey sk:selector.selectedKeys()){

            		//从selector上的已选择Key集中删除正在处理的SelctionKey

            			selector.selectedKeys().remove(sk);

            			//如果sk的对应通道包含客户端的连接请求

            			if(sk.isAcceptable()){

            				//调用accept方法接受连接，产生服务器端对应的SocketChannel

            				SocketChannel sc=server.accept();

            				//设置非阻塞模式

            				sc.configureBlocking(false);

            				//将该SocketSchannel也注册到selector

            				sc.register(selector, SelectionKey.OP_READ);

            				//将sk对应的Channel设置成准备接受	其他请求

            				sk.interestOps(SelectionKey.OP_ACCEPT);

            			}

            			//如果sk对应的通过有数据需要读取

            			if(sk.isReadable()){

            				//获取该SelectionKey对应Channel,该Channel中有可读的数据

            				SocketChannel sc=(SocketChannel) sk.channel();

            				//定义准备执行读取数据的ByteBuffer

            				ByteBuffer buff=ByteBuffer.allocate(1024);

            				String content="";

            				//开始读取数据

            			try {

							 while(sc.read(buff)>0){

            					buff.flip();

            					content+=charset.decode(buff);

            				}

							 //打印从该sk对应的Channel读取到的数据

							 System.out.println("===="+content);

							 //将sk对应的Channel设置成准备下一次读取

							 sk.interestOps(SelectionKey.OP_READ);

						}

            			//如果捕捉到该sk对应的Channel出现了异常，即表明该Channel

            			//对应的Client出现了异常，所以从Selector中取消sk的注册

            			catch (Exception e) {

            				//从Selector中删除指定的SelectionKey

            				sk.cancel();

            				if(sk.channel()!=null){

            					sk.channel().close();

            				}

						  }

            		//如果content的长度大于0	,即聊天信息不为空

            			if(content.length()>0){

            				//遍历该selector里注册的所有SelectKey

            				for(SelectionKey key:selector.keys()){

            					//获取该key对应的channel

            					Channel targetChannel=key.channel();

            					//如果该channle是SocketChannle对象

            					if(targetChannel instanceof SocketChannel){

            						//将读到的内容放入该Channel中

            						SocketChannel dest=(SocketChannel)targetChannel;

            						dest.write(charset.encode(content));  //客户端会读取该消息内容

            					}

            				}

            			}

             		}

            	}

            }

		}

	public static void main(String[] args) throws IOException {

		new NServer().init();

	}

}

客户端：

package com.net.scday3;

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.SocketChannel;

import java.nio.charset.Charset;

import java.util.Scanner;

public class NClient {

	//定义检测SocketChannel的Selector对象

	private  Selector selector=null;

	//定义处理编码和解码的字符集

	private Charset charset=Charset.forName("UTF-8");

	//客户端SocketChannel

	private SocketChannel sc=null;

	public void init() throws IOException{

		selector=Selector.open();

		InetSocketAddress isa=new InetSocketAddress("127.0.0.1",30000);

        //调用open静态方法创建连接到指定主机的SocketChannel

		sc=SocketChannel.open(isa);

		//设置该sc以非阻塞方式工作

		sc.configureBlocking(false);

		//将SocketChannel对象注册到指定Selector

		sc.register(selector, SelectionKey.OP_READ);

		//启动读取服务器端数据的线程

		new ClientThread().start();

		//创建键盘输入流

		Scanner scan=new Scanner(System.in);

		while(scan.hasNextLine()){

			//读取键盘输入

			String line=scan.nextLine();

			//将键盘输入的内容输出到SocketChannel中

			sc.write(charset.encode(line));

		}

	}

	//定义读取服务器端的线程

	private class ClientThread extends Thread{

		@Override

		public void run() {

			try {

				while (selector.select()>0){

					//遍历每个可用IO操作Channel对应的SelectionKey

					for(SelectionKey sk:selector.selectedKeys()){

						//删除正在处理的SelectionKey

						selector.selectedKeys().remove(sk);

						//如果该SeclectionKey对应的Channel有可读的数据

						if(sk.isReadable()){

							//使用NIO读取Channel	中的数据

							SocketChannel sc=(SocketChannel) sk.channel();

							ByteBuffer buff=ByteBuffer.allocate(1024);

							String content="";

							while(sc.read(buff)>0){

								sc.read(buff);

								buff.flip();

								content+=charset.decode(buff);

							}

							//打印输出读取的内容

							System.out.println("聊天信息:"+content);

							//为下一次读取做准备

							sk.interestOps(SelectionKey.OP_READ);

						}

					}

				}

			} catch (IOException e) {

				e.printStackTrace();

			}

		}

	}

	public static void main(String[] args) throws IOException {

		new NClient().init();

	}

}