使用JavaNIO实现简易在线多人聊天室

一、 服务端代码

package chatroom.server;

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;

/******
 @author 阿昌
 @create 2021-09-13 20:23
 聊天室服务端
 *******
 */
public class ChatServer {

    //服务端启动的方法
    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、为channel通道绑定端口号
        serverSocketChannel.bind(new InetSocketAddress(9090));
        serverSocketChannel.configureBlocking(false);//设置非阻塞模式

        //4、把serverSocketChannel绑定到selector上
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
        System.out.println("服务器启动.......");

        //5、循环监听是否有连接连入
        while (true) {
            int select = selector.select();

            //如果为0，则为没连接，没有获取到，就跳出循环
            if (select == 0) {
                continue;
            }

            //获取可用channel
            Set<SelectionKey> selectionKeys = selector.selectedKeys();
            //遍历
            Iterator<SelectionKey> iterator = selectionKeys.iterator();
            while (iterator.hasNext()) {
                SelectionKey selectionKey = iterator.next();

                //移除 set 集合当前 selectionKey
                iterator.remove();

                //6、根据就绪状态，调用对应方法实现具体业务操作
                if (selectionKey.isAcceptable()) {
                    //6.1 如果 accept 状态
                    acceptOperator(serverSocketChannel, selector);
                }
                if (selectionKey.isReadable()) {
                    //6.2 如果可读状态
                    readOperator(selector, selectionKey);
                }
            }
        }
    }

    //处理可读状态操作
    private void readOperator(Selector selector, SelectionKey selectionKey) throws IOException {
        //1 从 SelectionKey 获取到已经就绪的通道
        SocketChannel channel = (SocketChannel) selectionKey.channel();

        //2 创建 buffer
        ByteBuffer byteBuffer = ByteBuffer.allocate(1024);

        //3 循环读取客户端消息
        int readLength = channel.read(byteBuffer);
        String message = "";//用于接收解码后的信息

        //表示里面有数据
        if (readLength > 0) {
            //切换读模式
            byteBuffer.flip();
            //读取内容
            message += Charset.forName("UTF-8").decode(byteBuffer);
        }

        //4 将 channel 再次注册到选择器上，监听可读状态
        channel.register(selector, SelectionKey.OP_READ);

        //5 把客户端发送消息，广播到其他客户端
        if (message.length() > 0) {
            //广播给其他客户端
            System.out.println(message);
            castOtherClient(message, selector, channel);
        }
    }

    //广播到其他客户端
    private void castOtherClient(String message, Selector selector, SocketChannel channel) throws IOException {
        //1 获取所有已经接入 channel
        Set<SelectionKey> selectionKeySet = selector.keys();
        //2 循环想所有 channel 广播消息
        for (SelectionKey selectionKey : selectionKeySet) {
            //获取每个 channel
            Channel tarChannel = selectionKey.channel();
            //不需要给自己发送
            if (tarChannel instanceof SocketChannel && tarChannel != channel) {//不向自己广播
                ((SocketChannel) tarChannel).write(Charset.forName("UTF-8").encode(message));
            }
        }
    }


    //处理接入状态操作
    private void acceptOperator(ServerSocketChannel serverSocketChannel, Selector selector) throws IOException {
        //1 接入状态，创建 socketChannel
        SocketChannel accept = serverSocketChannel.accept();
        //2 把 socketChannel 设置非阻塞模式
        accept.configureBlocking(false);
        //3 把 channel 注册到 selector 选择器上，监听可读状态
        accept.register(selector, SelectionKey.OP_READ);
        //4 客户端回复信息
        accept.write(Charset.forName("UTF-8").encode("欢迎进入聊天室，请注意隐私安全"));
    }

    public static void main(String[] args) throws IOException {
        new ChatServer().startServer();
    }

}

---

二、客户端代码

package chatroom.client;

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;

/******
 @author 阿昌
 @create 2021-09-13 20:45
 聊天室客户端
 *******
 */
public class ChatClient {

    //启动方法
    public void startClient(String name) throws IOException {
        //连接服务端
        SocketChannel socketChannel = SocketChannel.open(new InetSocketAddress("127.0.0.1",9090));
        //接收服务端响应数据
        Selector selector = Selector.open();
        socketChannel.configureBlocking(false);//设置非阻塞连接
        socketChannel.register(selector, SelectionKey.OP_READ);//将通道注册到selector上
        //创建线程，来接收服务端的响应信息
        new Thread(new ClientThread(selector)).start();

        //向服务端发送信息
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNextLine()){
            String msg = scanner.nextLine();
            if (msg.length()>0){
                //写入通道消息，让他发送给服务端
                socketChannel.write(Charset.forName("UTF-8").encode(name+": "+msg));
            }
        }
    }

}

---

三、客户端异步监听服务端响应Runnable类

package chatroom.client;

import java.io.IOException;
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.Iterator;
import java.util.Set;

/******
 @author 阿昌
 @create 2021-09-13 20:57
 客户端异步监听服务端响应Runnable类
 *******
 */
public class ClientThread implements Runnable {

    private Selector selector;

    public ClientThread(Selector selector) {
        this.selector = selector;
    }

    @Override
    public void run() {
        try {
            while (true) {
                //获取 channel 数量
                int readChannels = selector.select();
                if (readChannels == 0) {
                    continue;
                }
                //获取可用的 channel
                Set<SelectionKey> selectionKeys = selector.selectedKeys();
                //遍历集合
                Iterator<SelectionKey> iterator = selectionKeys.iterator();
                while (iterator.hasNext()) {
                    SelectionKey selectionKey = iterator.next();
                    //移除 set 集合当前 selectionKey
                    iterator.remove();
                    //如果可读状态
                    if (selectionKey.isReadable()) {
                        //处理可读状态操作
                        readOperator(selector, selectionKey);
                    }
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }


    //处理可读状态操作
    private void readOperator(Selector selector, SelectionKey selectionKey) throws IOException {
        //1 从 SelectionKey 获取到已经就绪的通道
        SocketChannel socketChannel =(SocketChannel) selectionKey.channel();
        //2 创建 buffer
        ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
        //3 循环读取客户端消息
        int readLength = socketChannel.read(byteBuffer);
        String message = "";//用于存储解码后的消息
        if (readLength > 0) {
            //切换读模式
            byteBuffer.flip();
            //读取内容
            message += Charset.forName("UTF-8").decode(byteBuffer);
        }
        //4 将 channel 再次注册到选择器上，监听可读状态
        socketChannel.register(selector, SelectionKey.OP_READ);
        //5 把客户端发送消息，广播到其他客户端
        if (message.length() > 0) {
            //广播给其他客户端
            System.out.println(message);
        }
    }
    
}

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四、A/B客户端

• AClient

public class AClient {
    public static void main(String[] args) {
        try {
            new ChatClient().startClient("阿昌一号");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

• BClient

public class BClient {
    public static void main(String[] args) {
        try {
            new ChatClient().startClient("阿昌二号");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

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五、演示

服务端启动后，AClient和BClient都发送一条消息后的效果

• 服务端控制台

• AClient客户端控制台

• BClient客户端控制台

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