Network do the students, it is estimated will often use this function, make a record of it here.
First check specific port is occupied by:
sudo netstat -nplt
Second, you must delete and view a specific port:
kill -9 pid_num
sudo netstat -nplt
Here's the way to familiarize yourself with netstat parameters:
-a (all) to display all the options, not displayed by default LISTEN related
-t (tcp) display only tcp related options
-u (udp) Only udp related options
-n refused to display an alias, to show all converted into digital numbers.
-l Only lists service status in Listen (listen) of
-p establish links display the program name
-r Displays the routing information, routing table
-e displays extended information, such as for example uid
-s statistics by individual agreement
-c at intervals of a fixed time, the implementation of the netstat command.
Tip: LISTEN and LISTENING state with only -a or -l to see