socata# lsof -i tcp:25

#OUTPUT:

COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
master 1003 root 11u IPv4 0xc505c740 0t0 TCP dk.iaindooley.com:smtp (LISTEN)
master 1330 root 11u IPv4 0xc53fb1d0 0t0 TCP ap.iaindooley.com:smtp (LISTEN)
master 19196 root 11u IPv4 0xc505b570 0t0 TCP localhost.iaindooley.com:smtp (LISTEN)