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();
             }
         }

     }