程序在本地能跑起來且正常訪問，部署到linux服務器上，跑起來沒報錯，但是就是訪問不了，
這種問題往往是防火牆問題！！
下面是red hat/CentOs7關閉防火牆的命令：
1:查看防火狀態
systemctl status firewalld
service iptables status
2:暫時關閉防火牆
systemctl stop firewalld
service iptables stop
3:永久關閉防火牆
systemctl disable firewalld
chkconfig iptables off
4:重啟防火牆
systemctl enable firewalld
service iptables restart
5:永久關閉后重啟
chkconfig iptables on