Java-NIO（八）：DatagramChannel

Java NIO中的DatagramChannel是一个能收发UDP包的通道。
操作步骤：
　　1）打开 DatagramChannel
　　2）接收/发送数据

同样它也支持NIO的非阻塞模式操作,例如：

@Test
    public void send() throws IOException {
        DatagramChannel channel = DatagramChannel.open();
        channel.configureBlocking(false);

        ByteBuffer byteBuffer = ByteBuffer.allocate(1024);

        Scanner scanner = new Scanner(System.in);
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        while (scanner.hasNext()) {
            String line = scanner.next();
            byteBuffer.put((format.format(new Date()) + ":" + line).getBytes());
            byteBuffer.flip();

            channel.send(byteBuffer, new InetSocketAddress("127.0.0.1", 9899));
            byteBuffer.clear();
        }

        channel.close();
    }

    @Test
    public void receive() throws IOException {
        DatagramChannel channel = DatagramChannel.open();
        channel.configureBlocking(false);
        channel.bind(new InetSocketAddress(9899));

        Selector selector = Selector.open();
        channel.register(selector, SelectionKey.OP_READ);

        while (selector.select() > 0) {
            Iterator<SelectionKey> selectionKeys = selector.selectedKeys().iterator();
            while (selectionKeys.hasNext()) {
                SelectionKey selectionKey = selectionKeys.next();
                if (selectionKey.isReadable()) {
                    ByteBuffer buffer = ByteBuffer.allocate(1024);
                    channel.receive(buffer);
                    buffer.flip();
                    System.out.println(new String(buffer.array(), 0, buffer.limit()));
                    buffer.clear();
                }

                selectionKeys.remove();
            }
        }

    }