code: private void doListen() throws IOException {
  		while (0 != this.selector.select()) {
  			// 返回已选择键的集合
  			final Iterator<SelectionKey> keyIter = selector.selectedKeys().iterator();
  			while (keyIter.hasNext()) {
  				handle(keyIter.next());
  				keyIter.remove();
  			}
  		}
  	}
docs: 开始监听
  
  @throws IOException IO异常