the command "netstat -p" doesn't display the pid

Question

the shell command netstat -p , doesn't display the pid. It displays "-" like this:

tcp        0      0 *:2181 *:53837 ESTABLISHED -

why?

It still display "-" although I use root to login.

Answer 1

Use sudo to see all fields.

$ sudo netstat -p 

Also, I like to use sudo netstat -pant because it is easy to remember, and I'm almost always only interested in seeing the TCP info.