Netty学习——实战篇2 NIO 群聊系统（简单版）备份

需求：

1、编写一个NIO群聊系统，实现服务端和客户端之间数据简单通讯(非阻塞)

2、实现多人群聊

3、服务端：可以监测用户上线、离线、并实现消息转发功能。

4、客户端：通过channel可以无阻塞发送消息给其他所有用户，同时可以接受其他用户发送的消息。

5、目的：进一步理解NIO非阻塞网络编程机制

服务端代码：GroupChatServer.java

@Slf4j
public class GroupChatServer {
    //选择器
    private Selector selector;
    //监听器
    private ServerSocketChannel serverSocketChannel;
    //端口号
    private static final  int PORT = 8000;
    //构造方法，初始化成员变量
    public GroupChatServer(){
        try {
            //1 创建监听器
            serverSocketChannel = ServerSocketChannel.open();
            //2 创建选择器
            selector = Selector.open();
            //3 绑定端口号
            serverSocketChannel.socket().bind(new InetSocketAddress(PORT));
            //4 设置非阻塞模式
            serverSocketChannel.configureBlocking(false);
            //5 事件绑定
            serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
        }catch (Exception e){
            e.printStackTrace();
        }

    }

    //监听
    public void listen(){
        log.info("监听的线程号是:{}",Thread.currentThread().getId());
        try {
            //循环等待客户端连接
            while(true){
                int count  = selector.select();
                if(count > 0){
                    //表示有客户端连接
                    //遍历得到selectorKey
                    Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
                    while(iterator.hasNext()){
                        SelectionKey key = iterator.next();
                        //判断事件监听类型
                        if(key.isAcceptable()){
                            /*//事件：连接
                            SocketChannel socketChannel = serverSocketChannel.accept();
                            //设置为非阻塞
                            socketChannel.configureBlocking(false);
                            //把socketchannel的读取事件类型注册到选择器上
                            socketChannel.register(selector,SelectionKey.OP_READ);
                            //提示用户上线
                            log.info("用户，{}",socketChannel.getRemoteAddress(),"已上线");*/
                            accept(serverSocketChannel);
                        }
                        if(key.isReadable()){
                            readClientMessage(key);
                        }
                        iterator.remove();
                    }
                }else{
                    log.info("等待客户端连接");
                }
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {

        }

    }

    //客户端连接事件
    public void accept(ServerSocketChannel serverSocketChannel) throws Exception{
        //获取SocketChannel
        SocketChannel socketChannel = serverSocketChannel.accept();
        //设置SocketChannel 为非阻塞模式
        socketChannel.configureBlocking(false);
        //把读取事件绑定到选择器上
        socketChannel.register(selector,SelectionKey.OP_READ);
        //提示用户上线
        log.info("用户，{}，已上线",socketChannel.getRemoteAddress());
    }

    //读取客户端信息
    public void readClientMessage(SelectionKey key){
        SocketChannel socketChannel = null;
        try {
            //根据key获取SocketChannel
            socketChannel = (SocketChannel)key.channel();
            //创建ByteBuffer
            ByteBuffer buffer = ByteBuffer.allocate(1024);
            //channel 读取 buffer
            int count = socketChannel.read(buffer);
            //根据count的值做处理
            if(count > 0) {
                //把缓冲区的数据转换成字符串
                String msg = new String(buffer.array());
                //输出该消息
                log.info("来自客户端：{}, 的消息是:{}",socketChannel.getRemoteAddress(),msg);
                //向其他客户端转发消息(排除自己)
                sendMessageToOtherClients(msg,socketChannel);
            }


        }catch (Exception e){
            try {
                //提示离线
                log.info("{}",socketChannel.getRemoteAddress(),"：已下线");
                //取消注册
                key.cancel();
                //关闭通道
                socketChannel.close();
            }catch (Exception e2){
                e2.printStackTrace();
            }
        }
    }

    public void sendMessageToOtherClients(String message,SocketChannel socketChannel) throws Exception{
        log.info("消息转发中。。。");
        log.info("服务器发送数据给客户端的线程是:{}",Thread.currentThread().getId());
        //遍历所有注册到selector的SocketChannel，排除自己
        for(SelectionKey key : selector.keys()){
            //通过key取出对应的SocketChannel
            Channel targetChannel =  key.channel();
            //排除自己
            if(targetChannel instanceof SocketChannel &&  targetChannel != socketChannel){
                SocketChannel dest = (SocketChannel) targetChannel;
                //把消息存储到ByteBuffer
                ByteBuffer buffer = ByteBuffer.wrap(message.getBytes());
                //把buffer的数据写入通道
                dest.write(buffer);
            }

        }


    }

    public static void main(String[] args) {
        GroupChatServer server = new GroupChatServer();
        server.listen();
    }

}

客户端 GroupChatClient.java

@Slf4j
public class GroupChatClient {
    //服务器IP
    private static final String HOST = "127.0.0.1";
    //服务器端口号
    private static final int PORT = 8000;
    //选择器
    private Selector selector;
    //SocketChannel
    private SocketChannel socketChannel;
    //用户名
    private String username;
    //构造器
    public GroupChatClient() throws Exception{
        //获取selector
        selector = Selector.open();

        //连接到服务器
        socketChannel = socketChannel.open(new InetSocketAddress("127.0.0.1", PORT));
        //设置为非阻塞
        socketChannel.configureBlocking(false);
        //将channel的读事件注册到selector
        socketChannel.register(selector, SelectionKey.OP_READ);
        //初始化username
        username = socketChannel.getLocalAddress().toString().substring(1);
        log.info("{},客户端初始化完成",username);
    }

    //向服务器发送消息
    public void sendMessage(String message){
        message = username + " 说：" + message;
        try {
            socketChannel.write(ByteBuffer.wrap(message.getBytes()));
            //log.info("用户:{},说:{}",username,message);
        }catch (Exception e){
            e.printStackTrace();
        }
    }
    //读取从服务器获取的消息
    public void readMessage(){
        try {
            //获取socketChannel的通道数量
            int count = selector.select();
            //如果通道数量大于0，说明有可用的通道
            if(count > 0){
                //获取所有通道的迭代器
                Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
                //循环判断
                while(iterator.hasNext()){
                    //获取key
                    SelectionKey key = iterator.next();
                    //如果事件类型是读取类型
                    if(key.isReadable()){
                        //获取相关通道
                        SocketChannel channel = (SocketChannel) key.channel();
                        //创建Bytebuffer
                        ByteBuffer buffer = ByteBuffer.allocate(1024);
                        //读取buffer
                        channel.read(buffer);
                        //把读取到缓冲区的数据转换成字符串，并输出
                        String message = new String(buffer.array());
                        log.info("{}",message);
                    }

                }
                //删除当前的SelectionKey，方法重复注册
                iterator.remove();

            }

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

    public static void main(String[] args) throws Exception{
        //启动客户端
        GroupChatClient chatClient = new GroupChatClient();
        //启动一个线程，每隔3秒，从服务器读取数据
        new Thread(){
            public void run(){
                while(true){
                    chatClient.readMessage();
                    try {
                        Thread.currentThread().sleep(3000);
                    }catch (InterruptedException e){
                        e.printStackTrace();
                    }
                }
            }
        }.start();
        //发送数据到服务端
        Scanner scanner = new Scanner(System.in);
        while(scanner.hasNextLine()){
            String s = scanner.nextLine();
            chatClient.sendMessage(s);
        }
    }
}

服务端运行结果：