For more technical detail, https://linuxjournal.rubdos.be/ljarchive/LJ/298/12538.html https://linuxjournal.rubdos.be/ljarchive/LJ/298/12538.html goes into a TON

For more technical detail, https://linuxjournal.rubdos.be/ljarchive/LJ/298/12538.html https://linuxjournal.rubdos.be/ljarchive/LJ/298/12538.html goes into a TON more detail on this, including simplified code for the implementation of the which-socket-should-receive-this-packet algorithm. TL;DR: - the OS maintains a hash map mapping port/IP/protocol/protocol-version to lists of sockets - there's a scoring algorithm that determines which socket wins, based on specificity of how the socket(s) were bound - if multiple sockets are bound with SO_REUSEPORT, things are routed based on a hash of the source/destination address/port, presumably so packets from a single client aren't split between different handlers - essentially, simple zero-backpressure load balancing - read the article for nuances of when and how to use this, especially performance considerations about pre/post fork - consider adding TL;DR segments like this, whether you're writing discovery fiction like the OP, or technical deep-dives like the link in this comment. Different readers will prefer different formats, but everyone benefits from having the option to consume an abstract before reading lengthy nonfiction prose!