Alibaba Cloud lightweight server centos 7 cannot open the port

I have been troubled by a small problem for a long time, hereby record it

1. Open the port you need to open in the Alibaba Cloud console

2. firewall-cmd --zone=public --add-port=8889/tcp --permanent
   firewall-cmd --reload
   service firewalld restart

ps: No need to modify iptables in centos7