客户端

NioClient

public class NioClient {
    private static NioClientHandle nioClientHandle;
    public static void start(){
        nioClientHandle = new NioClientHandle(DEFAULT_SERVER_IP,DEFAULT_PORT);
        new Thread(nioClientHandle,"Server").start();
    }
    //向服务器发送消息
    public static boolean sendMsg(String msg) throws Exception{
        nioClientHandle.sendMsg(msg);
        return true;
    }
    public static void main(String[] args) throws Exception {
        start();
        Scanner scanner = new Scanner(System.in);
        while(NioClient.sendMsg(scanner.next())) {
        }
    }
}

NioClientHandle

public class NioClientHandle implements Runnable{
    private String host;
    private int port;
    private volatile boolean started;
    private Selector selector;
    private SocketChannel socketChannel;
    public NioClientHandle(String ip, int port) {
        this.host = ip;
        this.port = port;
        try {
            selector = Selector.open();
            socketChannel = SocketChannel.open();
            socketChannel.configureBlocking(false);
            started = true;
        } catch (Exception e){
            e.printStackTrace();
        }
    }
    public void stop(){
        started = false;
    }
    @Override
    public void run() {
        try{
            doConnect();
        }catch(IOException e){
            e.printStackTrace();
            System.exit(1);
        }
        //循环遍历selector
        while(started){
            try{
                //无论是否有读写事件发生，selector每隔1s被唤醒一次
                selector.select(1000);
                //获取当前有哪些事件可以使用
                Set<SelectionKey> keys = selector.selectedKeys();
                //转换为迭代器
                Iterator<SelectionKey> it = keys.iterator();
                SelectionKey key = null;
                while(it.hasNext()){
                    key = it.next();
                    /*我们必须首先将处理过的 SelectionKey 从选定的键集合中删除。
                    如果我们没有删除处理过的键，那么它仍然会在主集合中以一个激活
                    的键出现，这会导致我们尝试再次处理它。*/
                    it.remove();
                    try{
                        handleInput(key);
                    }catch(Exception e){
                        if(key != null){
                            key.cancel();
                            if(key.channel() != null){
                                key.channel().close();
                            }
                        }
                    }
                }
            }catch(Exception e){
                e.printStackTrace();
                System.exit(1);
            }
        }
        //selector关闭后会自动释放里面管理的资源
        if(selector != null) {
            try{
                selector.close();
            }catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
    // 具体的事件处理方法
    private void handleInput(SelectionKey key) throws IOException{
        if(key.isValid()){
            //获得关心当前事件的channel
            SocketChannel sc = (SocketChannel) key.channel();
            //连接事件
            if(key.isConnectable()){
                if(sc.finishConnect()){socketChannel.register(selector,
                        SelectionKey.OP_READ);}
                else {
                    System.exit(1);
                }
            }
            //有数据可读事件
            if(key.isReadable()){
                //创建ByteBuffer，并开辟一个1M的缓冲区
                ByteBuffer buffer = ByteBuffer.allocate(1024);
                //读取请求码流，返回读取到的字节数
                int readBytes = sc.read(buffer);
                //读取到字节，对字节进行编解码
                if(readBytes>0){
                    //将缓冲区当前的limit设置为position,position=0，
                    // 用于后续对缓冲区的读取操作
                    buffer.flip();
                    //根据缓冲区可读字节数创建字节数组
                    byte[] bytes = new byte[buffer.remaining()];
                    //将缓冲区可读字节数组复制到新建的数组中
                    buffer.get(bytes);
                    String result = new String(bytes,"UTF-8");
                    System.out.println("客户端收到消息：" + result);
                }
                //链路已经关闭，释放资源
                else if(readBytes<0){
                    key.cancel();
                    sc.close();
                }
            }
        }
    }
    private void doWrite(SocketChannel channel,String request)
            throws IOException {
        //将消息编码为字节数组
        byte[] bytes = request.getBytes();
        //根据数组容量创建ByteBuffer
        ByteBuffer writeBuffer = ByteBuffer.allocate(bytes.length);
        //将字节数组复制到缓冲区
        writeBuffer.put(bytes);
        //flip操作
        writeBuffer.flip();
        //发送缓冲区的字节数组
        /*关心事件和读写网络并不冲突*/
        channel.write(writeBuffer);
    }
    private void doConnect() throws IOException{
        if(socketChannel.connect(new InetSocketAddress(host,port))){
            socketChannel.register(selector, SelectionKey.OP_READ);
        }else{
            socketChannel.register(selector, SelectionKey.OP_CONNECT);
        }
    }
    //写数据对外暴露的API
    public void sendMsg(String msg) throws Exception{
        doWrite(socketChannel, msg);
    }
}