Louis Pouzin and the datagram revolution - Negative PID

One of the most important contributors to the modern Internet was Louis Pouzin, a French computer scientist whose CYCLADES network introduced ideas that would

Negative PID
Many thanks to @PowerDNS for this blog post on how to properly serve #datagrams while listening on a wildcard address. Particularly useful as "Unix Network Programming" from #Stevens and al. is unhelpful in that regard (their approach can be summarized as "Who cares if the reply does not come out of the same address as that of the destination of the request, as long as the destination of the reply is correct?" I care, that's who; because of stateful firewalls for a start)
https://blog.powerdns.com/2012/10/08/on-binding-datagram-udp-sockets-to-the-any-addresses
On binding datagram (UDP) sockets to the ANY addresses | PowerDNS Blog

For around 10 years now, people have been requesting that PowerDNS learn how to automatically listen on all available IP addresses.