虽然经常用这个命令，但总是对其中的参数作用不太清楚，记录下
what are functions of netstat?
netstat - Print network connections, routing tables, interface statistics, masquerade
connections, and multicast memberships(大意就是打印网络连接。路由表。接口数据，伪装的连接和多播的成员关系)
netstat的参数很多，记录下常用的
-t #代表tcp
-u #代表udp
-l #show only listening sockets
-a #show both listening and non-listening(for TCP this means established connections)
-n #show numerical addressed instead of trying to determine symbolic host,port or user names
-v #代表verbose
-p #show the PID and name of the program to which each socket belongs
-o #Include information related to networking timers
-C #print routing information from the route cache
-Z #If selinux enabled print selinx context
-g #display multicast group membership information for IPV4 and IPV6
-r #display the kernel routing tables
-e #display other/more information
咱们经常用的几个
netstat -lntup |grep "mysqld"
netstat -an|grep 22
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NOTE(可替代的其他命令展示)
This program is obsolete. Replacement for netstat is ss. Replacement for netstat -r
is ip route. Replacement for netstat -i is ip -s link. Replacement for netstat -g
is ip maddr.