Network Connections and Applications

A fairly common question is: How do I determine which applications are making network connections?

While there are different ways to do this, a quick solution is with netstat. To see which applications are connecting to which network addresses, run the following as root (if you are not root certain output is limited):

# netstat -tuap

This will produce several columns of output the last column is PID/Program name. If you do not recognize the application name, use the PID number and use the ps command to find more information. For example (replace PID with the actual number):

# ps -p PID -F

For more information on the many other functions of either of these commands use the man utility:

# man netstat
# man ps