[网络协议]DatagramChannel 数据传输

在java中使用UDP传输数据比TCP更加简单。和socket的TCP不同，UDP不是面向连接的协议。使用UDP时，只要知道服务器IP和端口就可以直接向对方发送数据。在java中使用DatagramChannel来处理UDP的数据传输。
在服务端，首先调用bind()方法绑定DatagramChannel的监听端口。当数据来到时调用了revice()方法，DatagramChannel接收数据后曦儿ByteBuffer缓冲区。

public class UDPClient {

    public static void main(String[] args) {
        new UDPClient().send();
    }
    @SneakyThrows
    public void send() {
        DatagramChannel channel = DatagramChannel.open();
        //设为非阻塞模式
        channel.configureBlocking(false);
        ByteBuffer buffer = ByteBuffer.allocate(1024);
        Scanner scanner = new Scanner(System.in);
        log.info("UDP客户端启动成功！");
        log.info("请输入发送内容：");
        while (scanner.hasNext()) {
            String next = scanner.next();
            Date date = new Date();
            buffer.put((date + ">>"+next).getBytes());
            buffer.flip();
            channel.send(buffer, new InetSocketAddress("127.0.0.1", 8888));
            buffer.clear();
        }
        channel.close();
    }
}

    @SneakyThrows
    public void receive(){
        DatagramChannel channel = DatagramChannel.open();
        //设置为非阻塞模式
        channel.configureBlocking(false);
        //绑定监听地址
        channel.bind(new InetSocketAddress("127.0.0.1",8888));
        //开启选择器
        Selector selector = Selector.open();
        //将通道注册到选择器
        channel.register(selector,SelectionKey.OP_READ);
        //通过选择器查询IO时间
        while (selector.select()>0){
            Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
            ByteBuffer buffer = ByteBuffer.allocate(1024);
            while (iterator.hasNext()){
                SelectionKey selectionKey = iterator.next();
                //可读事件，有数据到来
                if(selectionKey.isReadable()){
                    //读取DatagramChannel 数据
                    SocketAddress address = channel.receive(buffer);
                    buffer.flip();
                    log.info(new String(buffer.array(),0,buffer.limit()));
                    buffer.clear();
                }
            }
            iterator.remove();
        }
        //关闭选择器和通道
        selector.close();
        channel.close();
    }