NIO群聊（纯代码）

• 客户端

package com.darwin.netty.nio.groupchat;

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.util.Iterator;
import java.util.Scanner;

/**
 * 群聊客户端
 *
 * @author yanghang
 */
public class GroupChatClient {

    private Selector selector;
    private SocketChannel socketChannel;
    private final static int SERVER_PORT = 6667;
    private final static String SERVER_ADDRESS = "127.0.0.1";
    private String userName;

    // 初始化
    public GroupChatClient () throws IOException {
        selector = Selector.open();
        // 连接服务端
        socketChannel = SocketChannel.open(new InetSocketAddress(SERVER_ADDRESS, SERVER_PORT));
        // 设置非阻塞
        socketChannel.configureBlocking(false);
        // 将Channel设置到selector上
        socketChannel.register(selector, SelectionKey.OP_READ);
        // 获取userName
        userName = socketChannel.getLocalAddress().toString().substring(1);
        System.out.println(userName + " is Ok");
    }

    // 向服务器发送信息
    public void sendInfo (String info) {
       info = userName + " : " + info;
        try {
            socketChannel.write(ByteBuffer.wrap(info.getBytes()));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    // 读取从服务器返回的消息
    public void readInfo () {
        try {

            int readChannels = selector.select();
            if(readChannels > 0) {//有可以用的通道

                Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
                while (iterator.hasNext()) {

                    SelectionKey key = iterator.next();
                    if(key.isReadable()) {
                        //得到相关的通道
                        SocketChannel sc = (SocketChannel) key.channel();
                        //得到一个Buffer
                        ByteBuffer buffer = ByteBuffer.allocate(1024);
                        //读取
                        sc.read(buffer);
                        //把读到的缓冲区的数据转成字符串
                        String msg = new String(buffer.array());
                        System.out.println(msg.trim());
                    }
                }
                //删除当前的selectionKey, 防止重复操作
                iterator.remove();
            }
        }catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) throws Exception {
        // 启动客户端,不断的读取信息
        GroupChatClient client = new GroupChatClient();

        new Thread(() -> {
            for (; ; ) {
                client.readInfo();
                try {
                    Thread.sleep(2000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }).start();

        //发送数据给服务器端
        Scanner scanner = new Scanner(System.in);

        while (scanner.hasNextLine()) {
            String s = scanner.nextLine();
            client.sendInfo(s);
        }
    }
}

• 服务端

package com.darwin.netty.nio.groupchat;

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

/**
 * 群聊服务端
 *
 * @author yanghang
 */
public class GroupChatServer {

    private Selector selector;
    private ServerSocketChannel serverSocketChannel;
    private final static int PORT = 6667;

    public GroupChatServer() {
        try {
            selector = Selector.open();
            serverSocketChannel = ServerSocketChannel.open();
            // 绑定端口
            serverSocketChannel.socket().bind(new InetSocketAddress(PORT));
            // 设置非阻塞
            serverSocketChannel.configureBlocking(false);
            // 将serverSocketChannel注册到selector
            serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);

        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    public void listen() {

        try {
        // 监听
        for (; ; ) {
            int select = selector.select();
            if (select > 0) {
               // 有事件要处理
                Set<SelectionKey> selectionKeys = selector.selectedKeys();
                Iterator<SelectionKey> iterator = selectionKeys.iterator();
                while (iterator.hasNext()) {
                    SelectionKey key = iterator.next();
                    if (key.isAcceptable()) {
                        // 有新的客户端连接
                        SocketChannel socketChannel = serverSocketChannel.accept();
                        socketChannel.configureBlocking(false);
                        // 将SocketChannel注册到selector上面
                        socketChannel.register(selector, SelectionKey.OP_READ);

                        System.out.println(socketChannel.getRemoteAddress() + " 上线");
                    }

                    if (key.isReadable()) {
                        readData(key);
                    }

                    iterator.remove();
                }
            }
        }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void readData(SelectionKey key) {
        // 获取关联的Channel
        SocketChannel socketChannel = null;
        try {
            socketChannel = (SocketChannel)key.channel();
            ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
            int read = socketChannel.read(byteBuffer);
            if (read > 0) {
               // 把缓冲区的转换为字符串
               String msg = new String(byteBuffer.array());
               System.out.println("from 客户端: " + msg);
               // 向其他的客户端发送消息
               sendOtherClient(msg, socketChannel);
            }
        } catch (IOException ex) {
            try {
                System.out.println(socketChannel.getRemoteAddress() + " 离线了..");
                //取消注册
                key.cancel();
                //关闭通道
                socketChannel.close();
            }catch (IOException e2) {
                e2.printStackTrace();;
            }
        }
    }

    private void sendOtherClient(String msg, SocketChannel socketChannel) throws IOException {
        Set<SelectionKey> keys = selector.keys();
        for (SelectionKey key:keys) {
            SelectableChannel selectableChannel = key.channel();
            if (selectableChannel instanceof SocketChannel && selectableChannel != socketChannel) {
                SocketChannel channel = (SocketChannel)selectableChannel;
                // 发送信息
                channel.write(ByteBuffer.wrap(msg.getBytes()));
            }
        }
    }

    public static void main(String[] args) {
        // 创建服务端处理器
        GroupChatServer server = new GroupChatServer();
        server.listen();
    }

}