1、查看防火墙
firewall-cmd --state

2、关闭防火墙
systemctl stop firewalld

3、开启防火墙
systemctl start firewalld

4、重启防火墙
systemctl restart firewalld

5、开放指定端口
sudo firewall-cmd --zone=public --add-port=3000/tcp --permanent
sudo firewall-cmd --reload