Using netstat

I use

# netstat -pant4

all the time to see what is listening/connected to my computer.
I found some other useful commands I didn't know about at http://openmaniak.com/netstat.php

To display all the opened network sockets (extended informations):

#netstat -aute
-a: All
-u: UDP
-t: TCP
-e: Extended

To display the summary statistics for each protocol

#netstat -s
-s: Summary statistics for each protocol.

To display the extended interfaces statistics:

#netstat -ie
-i: Interface
-e: Extended information