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：

 1 @Test
 2     public void send() throws IOException {
 3         DatagramChannel channel = DatagramChannel.open();
 4         channel.configureBlocking(false);
 5
 6         ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
 7
 8         Scanner scanner = new Scanner(System.in);
 9         SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
10         while (scanner.hasNext()) {
11             String line = scanner.next();
12             byteBuffer.put((format.format(new Date()) + ":" + line).getBytes());
13             byteBuffer.flip();
14
15             channel.send(byteBuffer, new InetSocketAddress("127.0.0.1", 9899));
16             byteBuffer.clear();
17         }
18
19         channel.close();
20     }
21
22     @Test
23     public void receive() throws IOException {
24         DatagramChannel channel = DatagramChannel.open();
25         channel.configureBlocking(false);
26         channel.bind(new InetSocketAddress(9899));
27
28         Selector selector = Selector.open();
29         channel.register(selector, SelectionKey.OP_READ);
30
31         while (selector.select() > 0) {
32             Iterator<SelectionKey> selectionKeys = selector.selectedKeys().iterator();
33             while (selectionKeys.hasNext()) {
34                 SelectionKey selectionKey = selectionKeys.next();
35                 if (selectionKey.isReadable()) {
36                     ByteBuffer buffer = ByteBuffer.allocate(1024);
37                     channel.receive(buffer);
38                     buffer.flip();
39                     System.out.println(new String(buffer.array(), 0, buffer.limit()));
40                     buffer.clear();
41                 }
42
43                 selectionKeys.remove();
44             }
45         }
46
47     }