# Show listening sockets.
# -t / --tcp : Show TCP sockets.
# -u / --udp : Show UDP sockets.
# -l : Show listening sockets.
# -p : Show pid.
#   NOTE: Ports open by the kernel won't show up with
#   program name.  NFS is a common culprit here.
# -n / --numeric : Show numerical addresses instead of trying to determine symbolic host, port or user names.
# -W / --wide : Do not truncate IP addresses by using output as wide as needed.
# -e / --extend : Display additional information.  Use this option twice for maximum detail.
# -o / --timers : Include information related to networking timers.
netstat -tulpn