Nio 实现多人聊天

1.服务器端

package nio;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.security.PublicKey;
import java.util.Iterator;

/**
 * Nio 聊天服务器
 */
public class GroupChatServer {
    private Selector selector;
    private ServerSocketChannel serverSocketChannel;
    private  static  final  int port=9000;
    /**
     * 构造方法
     * 初始化工作
     */
    public  GroupChatServer(){
    try{
        //得到选择器
        selector =Selector.open();
        //初始化 serverSocketChannel
        serverSocketChannel=ServerSocketChannel.open();
        //绑定端口
        serverSocketChannel.socket().bind(new InetSocketAddress(port));
        //设置非阻塞模式
        serverSocketChannel.configureBlocking(false);
        //将serverSocketChannel 注册到selector上
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);


    }catch (IOException e){
        e.printStackTrace();
    }
    }
    //监听
    public void listen(){
        try{
            while (true){//查询连接
                int count = selector.select();
                if(count>0){
                    //有事件处理
                    //得到连接集合遍历
                    Iterator<SelectionKey> keys = selector.selectedKeys().iterator();
                    SelectionKey selectionKey;
                    while (keys.hasNext()){
                         selectionKey = keys.next();
                         //如果监听到accept
                         if(selectionKey.isAcceptable()){
                             SocketChannel sc = serverSocketChannel.accept();
                             sc.configureBlocking(false);
                             //将该 sc注册到selector
                             sc.register(selector,SelectionKey.OP_READ);
                            //提示
                             System.out.println(sc.getRemoteAddress().toString().substring(1)+"上线");
                         }
                         if(selectionKey.isReadable()){
                             //如果通道时可读事件
                             readData(selectionKey);
                         }
                         //删除当前key，防止重复
                        keys.remove();
                    }

                }else {
                    System.out.println("等待客户端连接中。。。。");
                }
            }

        }catch (Exception e){
            e.printStackTrace();
        }finally {

        }
    }
    //读取客户端消息
    private void readData(SelectionKey ky){
        //定义 SocketChannel
        SocketChannel socketChannel=null;
        try{
            socketChannel=(SocketChannel)ky.channel();
            //创建buffer
            ByteBuffer buffer=ByteBuffer.allocate(1024);
            int len = socketChannel.read(buffer);
            if(len>0){
                //读取到了数据
                String s = new String(buffer.array());
                System.out.println("客户端："+s);
                //向其他客户端转发消息
                sendMsgToOtherClients(s,socketChannel);
            }
        }catch (IOException e){
            try {
                System.out.println(socketChannel.getRemoteAddress() + "离线了。。。");
                //取消注册
                ky.cancel();
                //关闭通道
                socketChannel.close();
            }catch (IOException e1){
                e1.printStackTrace();
            }
        }
    }
    //转发消息给其他客户端(通道)
    private  void sendMsgToOtherClients(String msg,SocketChannel client) throws  IOException{
        System.out.println("服务器转发消息");
        //遍历所有注册到select上的SocketChannel ，并排除自己
        for (SelectionKey k:selector.keys()){
            //通过key取出对应的
            //这里可以不用强转为 SocketChannel
        Channel tarChannel = k.channel();
         //   SocketChannel tarChannel =(SocketChannel) k.channel();
            //排除自己
            if(tarChannel instanceof SocketChannel&&tarChannel!=client){
                //转型
                SocketChannel  dest=(SocketChannel)tarChannel;
                //将信息msg存储到buffer
                ByteBuffer buffer = ByteBuffer.wrap(msg.getBytes());
                //将buffer写入通道中
                dest.write(buffer);
            }
        }
    }
    public static void main(String[] args) {
        GroupChatServer groupChatServer=new GroupChatServer();
        groupChatServer.listen();
    }
}

2.客户端

package nio;

import com.sun.org.apache.xerces.internal.util.SynchronizedSymbolTable;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectableChannel;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
import java.util.Scanner;

/**
 * Nio 客户端
 */
public class GroupChatClient {
    private final  String IP="127.0.0.1";
    private final  int port=9000;
    private Selector selector;
    private SocketChannel socketChannel;
    private  String userName;
    public  GroupChatClient() throws IOException {
        selector=Selector.open();
        //连接服务器
        socketChannel=socketChannel.open(new InetSocketAddress(IP,port));
        //设置非阻塞
        socketChannel.configureBlocking(false);
        //注册
        socketChannel.register(selector, SelectionKey.OP_READ);
        userName = socketChannel.getLocalAddress().toString().substring(1);
        System.out.println("客户端 "+userName+" 准备好了");
    }
    //向服务器发送消息
    public  void  sendMsg(String msg) throws IOException {
        msg=userName+"说："+msg;
        socketChannel.write(ByteBuffer.wrap(msg.getBytes()));
    }
    //读取从服务器端发送过来的消息
    public  void  readMsg() throws IOException {
        int readChannel = selector.select();
        if(readChannel>0){
            //有可用的通道
            Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
            while (iterator.hasNext()){
                SelectionKey k = iterator.next();
                if(k.isReadable()){
                    //得到相关的通道了
                    SocketChannel channel = (SocketChannel)k.channel();
                    ByteBuffer buffer = ByteBuffer.allocate(1024);
                    channel.read(buffer);
                    //把独到的缓冲区的数据转为字符串
                    System.out.println(new String(buffer.array()).trim());

                }

            }

            iterator.remove();// 删除当前的key防止重复操作
        }else {
            System.out.println("没有可用的通道。。。。");
        }

    }
    public static void main(String[] args) throws IOException {
        //启动客户端
        GroupChatClient chatClient=new GroupChatClient();
        //启动一个线程
        new Thread(new Runnable() {
            @Override
            public void run() {
                while (true){
                    try {
                        chatClient.readMsg();
                        Thread.currentThread().sleep(1000);
                    } catch (IOException e){
                        e.printStackTrace();
                    }catch (InterruptedException e1 ) {
                        e1.printStackTrace();
                    }
                }
            }
        }).start();
        //发送数据给服务器
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNextLine()){
            chatClient.sendMsg(scanner.nextLine());
        }

    }
}

运行效果