服务端实现

package com.bierce.io;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.nio.charset.Charset;
import java.util.Iterator;
import java.util.Set;
//服务器端
public class NIOChatServer {
public static void main(String[] args) {
	try {
		new NIOChatServer().startServer(); //启动服务器
	} catch (IOException e) {
		throw new RuntimeException(e);
	}
}
//服务端启动方法
public void startServer() throws IOException {
	//1. 创建Selector选择器
	Selector selector = Selector.open();
	//2.创建ServerSocketChannel通道
	ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
	//3.channel通道绑定监听端口,并设置为非阻塞模式
	serverSocketChannel.bind(new InetSocketAddress(8000));
	serverSocketChannel.configureBlocking(false);
	//4.channel注册到selector上,设置为就绪接收状态
	serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
	System.out.println("Server starts Successfully!");
	//5.自旋,实时监听客户端状态
	for (;;) {
		//获取所有就绪的Channel
		int readChannels = selector.select();
		if (readChannels == 0){ //没有接入的客户端
			continue;
		}
		Set<SelectionKey> selectionKeys = selector.selectedKeys();
		//遍历可用的Channel
		Iterator<SelectionKey> iterator = selectionKeys.iterator();
		while (iterator.hasNext()){
			SelectionKey selectionKey = iterator.next();
			//6.根据就绪状态,调用对应方法实现具体业务操作
			//6.1 accept状态
			if (selectionKey.isAcceptable()){
				acceptOperator(serverSocketChannel,selector);
			}
			//6.2 readable状态
			if (selectionKey.isReadable()){
				readOperator(selector,selectionKey);
			}
			iterator.remove(); //获取成功后没有必要保留需要移除
		}
	}
}
//处理可读状态的方法实现
private void readOperator(Selector selector, SelectionKey selectionKey) throws IOException {
	//从SelectionKey获取到已经就绪的通道
	SocketChannel socketChannel = (SocketChannel)selectionKey.channel();
	ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
	//自旋读取客户端信息
	int readLength = socketChannel.read(byteBuffer);
	String message = "";
	if (readLength > 0){
		byteBuffer.flip(); //切换读模式
		message += Charset.forName("UTF-8").decode(byteBuffer);
	}
	//注册channel到selector,监听可读状态
	socketChannel.register(selector, SelectionKey.OP_READ);
	if (message.length() > 0){
		//把客户端发送过来的信息广播到其他客户端
		System.out.println(message);
		castOtherClients(message,selector,socketChannel);
	}
}
//把客户端发送的消息广播给其他客户端
private void castOtherClients(String message, Selector selector, SocketChannel socketChannel) throws IOException {
	//获取所有已经接入的Channel
	Set<SelectionKey> selectionKeys = selector.keys();
	//对除自己以外的channel进行广播
	for (SelectionKey selectionKey:selectionKeys) {
		//获取每个Channel
	   Channel targetChannel = selectionKey.channel();
	   if (targetChannel instanceof SocketChannel && targetChannel != socketChannel){ //排除服务器以及发送方客户端自己
		   ((SocketChannel) targetChannel).write(Charset.forName("UTF-8").encode(message));
	   }
	}
}
//处理可接收状态的方法实现
private void acceptOperator(ServerSocketChannel serverSocketChannel, Selector selector) throws IOException {
	//接入状态：创建socketChannel
	SocketChannel socketChannel = serverSocketChannel.accept();
	//socketChannel设置为非阻塞并注册到selector上
	socketChannel.configureBlocking(false);
	socketChannel.register(selector,SelectionKey.OP_READ);
	//回复给客户端信息
	socketChannel.write(Charset.forName("UTF-8")
			.encode("Welcome to MyChatRoom, Please notice your Info!")); //UTF-8编码
}
}

客户端实现

package com.bierce.io;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.util.Scanner;
//客户端实现
public class NIOChatClient {
public void startClient(String name) throws IOException {
	//客户端连接服务器端
	SocketChannel socketChannel =
			SocketChannel.open(new InetSocketAddress("127.0.0.1",8000));
	//接收服务器端响应数据
	Selector selector = Selector.open();
	socketChannel.configureBlocking(false);
	socketChannel.register(selector, SelectionKey.OP_READ);
	//创建客户端线程
	new Thread(new ClientThread(selector)).start();
	//模拟向服务器发送消息
	Scanner sc = new Scanner(System.in);
	while (sc.hasNextLine()){
		String msg = sc.nextLine();
		if (msg.length() >0){
			socketChannel.write(Charset.forName("UTF-8").encode(name + "：" + msg));
		}
	}
}
}
class ClientThread implements Runnable{
    private Selector selector;
    public ClientThread(Selector selector) {
        this.selector = selector;
    }
    @Override
    public void run() {
        try {
            for (;;) {
                //获取所有就绪的Channel
                int readChannels = selector.select();
                if (readChannels == 0){ //没有接入的客户端
                    continue;
                }
                Set<SelectionKey> selectionKeys = selector.selectedKeys();
                //遍历可用的Channel
                Iterator<SelectionKey> iterator = selectionKeys.iterator();
                while (iterator.hasNext()){
                    SelectionKey selectionKey = iterator.next();
                    iterator.remove(); //获取成功后没有必要保留需要移除
                    //readable状态
                    if (selectionKey.isReadable()){
                        readOperator(selector,selectionKey);
                    }
                }
            }
        }catch (Exception e){
            e.printStackTrace();
        }
    }
    //处理可读状态的方法实现
    private void readOperator(Selector selector, SelectionKey selectionKey) throws IOException {
        //从SelectionKey获取到已经就绪的通道
        SocketChannel socketChannel = (SocketChannel)selectionKey.channel();
        ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
        //自旋读取客户端信息
        int readLength = socketChannel.read(byteBuffer);
        String message = "";
        if (readLength > 0){
            byteBuffer.flip(); //切换读模式
            message += Charset.forName("UTF-8").decode(byteBuffer);
        }
        //注册channel到selector,监听可读状态
        socketChannel.register(selector, SelectionKey.OP_READ);
        if (message.length() > 0){
            System.out.println(message); //该客户端控制台输出服务端发送过来的信息
        }
    }
}

//客户端A
package com.bierce.io;
import java.io.IOException;
public class TestAClient {
    public static void main(String[] args) {
        try {
            new NIOChatClient().startClient("A");
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
}
//客户端B
package com.bierce.io;
import java.io.IOException;
public class TestBClient {
    public static void main(String[] args) {
        try {
            new NIOChatClient().startClient("B");
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
}

效果图