sudo lsof -i tcp:80

COMMAND  PID     USER   FD   TYPE DEVICE SIZE/OFF NODE NAME  
nginx   1858     root    6u  IPv4   5043      0t0  TCP ruir.mxxx.com:http (LISTEN)  
nginx   1867 www-data    6u  IPv4   5043      0t0  TCP ruir.mxxx.com:http (LISTEN)  
nginx   1868 www-data    6u  IPv4   5043      0t0  TCP ruir.mxxx.com:http (LISTEN)  
nginx   1869 www-data    6u  IPv4   5043      0t0  TCP ruir.mxxx.com:http (LISTEN)  
nginx   1871 www-data    6u  IPv4   5043      0t0  TCP ruir.mxxx.com:http (LISTEN)