Centos7防火墙

1.关闭防火墙  firewall
    systemctl stop firewalld.service
    systemctl disable firewalld.service
    systemctl mask firewalld.service
    
 2. 安装iptables防火墙     
     yum install iptables-services -y

3.启动设置防火墙   
    systemctl start iptables

4. 查看防火墙状态
    systemctl status iptables

5. 编辑防火墙，增加端口
    vim /etc/sysconfig/iptables #编辑防火墙配置文件
     -A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT
     -A INPUT -m state --state NEW -m tcp -p tcp --dport 80 -j ACCEPT
     -A INPUT -m state --state NEW -m tcp -p tcp --dport 3306 -j ACCEPT
     :wq         #保存退出

6. 重启配置，重启系统
    systemctl restart iptables  #重启防火墙使配置生效
    systemctl enable iptables  #设置防火墙开机启动

7. 调试3306端口是否能登陆上去
    sudo iptables -L -n

 最后：实在不行 关闭防火墙
     systemctl disable iptables
     systemctl stop iptables

并：设置重启后自动关闭防火墙
    systemctl disable iptables