Finding of the process using a specific port

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

- You can also use the same invocation you're currently using:

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

-You can also use lsof:

$ sudo lsof -n -i :80 | grep LISTEN
nginx   125004 mhi    3u  IPv4   6645      0t0  TCP 0.0.0.0:80 (LISTEN)