check which process uses what port in linux code example

Example 1: linux query port use by pid

$ sudo netstat -nlp | grep :80
tcp  0  0  0.0.0.0:80  0.0.0.0:*  LISTEN  125004/nginx

Example 2: how to open port by fuser

root@exampleuser-X55CR:~# fuser -k  123/tcp
123/tcp:             11543