http://superuser.com/a/529844 (net-stat is deprecated)
http://www.cyberciti.biz/faq/how-do-i-find-out-what-ports-are-listeningopen-on-my-linuxfreebsd-server/
# nmap -sS -O 127.0.0.1
# lsof -i
# netstat -lptu
# netstat -tulpnsudo -u www-data php occ maintenance:install