JavaNIO实例UDP发送接收数据代码分享-创新互联

Java的NIO包中，有一个专门用于发送UDP数据包的类：DatagramChannel，UDP是一种无连接的网络协议，
一般用于发送一些准确度要求不太高的数据等。

完整的服务端程序如下：

public class StatisticsServer {
  //每次发送接收的数据包大小
  private final int MAX_BUFF_SIZE = 1024 * 10;
  //服务端监听端口，客户端也通过该端口发送数据
  private int port;
  private DatagramChannel channel;
  private Selector selector;
  private ScheduledExecutorService es = Executors.newScheduledThreadPool(1);
  public void init() throws IOException {
    //创建通道和选择器
    selector = Selector.open();
    channel = DatagramChannel.open();
    //设置为非阻塞模式
    channel.configureBlocking(false);
    channel.socket().bind(new InetSocketAddress(port));
    //将通道注册至selector，监听只读消息（此时服务端只能读数据，无法写数据）
    channel.register(selector, SelectionKey.OP_READ);
    //使用线程的方式，保证服务端持续等待接收客户端数据
    es.scheduleWithFixedDelay(new Runnable() {
      @Override
      public void run() {
        try {
          while(selector.select() > 0) {
            Iterator iterator = selector.selectedKeys().iterator();
            while(iterator.hasNext()) {
              SelectionKey key = iterator.next();
              try {
                iterator.remove();
                if(key.isReadable()) {
                  //接收数据
                  doReceive(key);
                }
              } catch (Exception e) {
                logger.error("SelectionKey receive exception", e);
                try {
                  if (key != null) {
                    key.cancel();
                    key.channel().close();
                  }
                } catch (ClosedChannelException cex) {
                  logger.error("Close channel exception", cex);
                }
              }
            }
          }
        } catch (IOException e) {
          logger.error("selector.select exception", e);
        }
      }
    }, 0L, 2L, TimeUnit.MINUTES);
  }
  //处理接收到的数据
  private void doReceive(SelectionKey key) throws IOException {
    String content = "";
    DatagramChannel sc = (DatagramChannel) key.channel();
    ByteBuffer buffer = ByteBuffer.allocate(MAX_BUFF_SIZE);
    buffer.clear();
    sc.receive(buffer);
    buffer.flip();
    while(buffer.hasRemaining()) {
      byte[] buf = new byte[buffer.limit()];
      buffer.get(buf);
      content += new String(buf);
    }
    buffer.clear();
    logger.debug("receive content="+content);
    if(StringUtils.isNotBlank(content)) {
      doSave(content);
    }
  }
 }