[root@ubuntu ~]# lsof -i:80
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
apache2 1220 root 4u IPv6 38019 0t0 TCP *:http (LISTEN)
apache2 1225 www-data 4u IPv6 38019 0t0 TCP *:http (LISTEN)
apache2 1226 www-data 4u IPv6 38019 0t0 TCP *:http (LISTEN)

[root@ubuntu ~]# fuser -k -9 80/tcp
80/tcp: 1220 1225 1226

[root@ubuntu ~]# lsof -i:80