参考：20 Netstat Commands for Linux Network Management
Foreword
Print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships
Options
-a：Show both listening and non-listening (for TCP this means established connections) sockets
-at：列出Active Internet connections (servers and established)
-au：列出Active Internet connections (servers and established)
-ax：列出Unix domain sockets
-l：Show only listening sockets.
-lt：列出Active Internet connections (only servers)
-lu：列出Active Internet connections (only servers)
-lx：列出Unix domain sockets
-s：Display summary statistics for each protocol.
-p：Show the PID and name of the program to which each socket belongs.
-c #：This will cause netstat to print the selected information every # seconds continuously.
-r：Display the kernel routing tables
-I=iface , -i：Display a table of all network interfaces, or the specified iface.
-ie：similar to ifconfig
