1. Turn off the firewall
systemctl stop firewalld
2. Turn on the firewall
systemctl start firewalld 开启防火墙
3. Check the firewall status
systemctl status firewalld
4. Open the specified port
firewall-cmd --zone=public --add-port=123/tcp --permanent
firewall-cmd --reload 重新载入
firewall-cmd --query-port=123/tcp查看端口是否开放成功
5. view all open ports
firewall-cmd --zone=public --list-ports