docs: public void handler(Packet packet, ChannelContext channelContext) throws Exception {
          SimplePacket pack = (SimplePacket) packet;
          byte[] body = pack.getBody();
          if(body!=null){
              String s = new String(body, SimplePacket.CHARSET);
              System.out.println("接受到客户端消息:"+s);
              SimplePacket resp = new SimplePacket();
              resp.setBody(("我收到了您的消息:"+s).getBytes());
              Tio.send(channelContext,resp);
          }
      }