how to use netstat to query for an specific port code example

Example 1: linux query port use by pid

$ sudo ss -lptn 'sport = :80'
State   Local Address:Port  Peer Address:Port              
LISTEN  127.0.0.1:80        *:*                users:(("nginx",pid=125004,fd=12))
LISTEN  ::1:80              :::*               users:(("nginx",pid=125004,fd=11))

Example 2: search by netstat by port

sudo netstat -nap | grep :80
or
sudo lsof -i:80