!!! deprecated (use ss instead)

2023
https://linuxhandbook.com/netstat-command/
2021
https://www.tecmint.com/20-netstat-commands-for-linux-network-management/

netstat
  https://hostpresto.com/community/tutorials/netstat-command-line-tips-and-tricks/
    -tulnp
    -tulanp - show open ports
    -lnp - ...