netstat命令不可用，安裝net-tools
有本地yum源或可連外網的yum源：直接yum安裝
yum install net-tools
沒有外網或本地yum源，下載rpm文件
如：net-tools-2.0-0.22.20131004git.el7.x86_64.rpm
wget https://centos.pkgs.org/7/centos-x86_64/net-tools-2.0-0.22.20131004git.el7.x86_64.rpm.html
安裝即可：
rpm -ivh net-tools-2.0-0.22.20131004git.el7.x86_64.rpm