linux check what process is using port

C++
$ sudo netstat -nlp | grep :80
tcp  0  0  0.0.0.0:80  0.0.0.0:*  LISTEN  125004/nginx
sudo lsof -i:22sudo lsof -i:<port_number>sudo ss -lptn 'sport = :80'$ netstat -ltnp | grep -w ':80' 
lsof -i tcp:53 #Check what is listening on port 53
lsof -t -i tcp:53 #Return the process PID listening on port 53
Source

Also in C++: