With SO_REUSEPORT option, multiple TCP server processes could bind() to the same server endpoint. Designed for the busiest multithreaded servers.
http://i.dailymail.co.uk/i/pix/2011/03/03/article-1362552-0D7319F3000005DC-882_634x357.jpg – a bunch of hungry chicks competing to get the next worm the mother delivers. The mother can only give the worm to one chick at a time. SO_REUSEPORT option sets up a chick family. When an incoming connection hits the accept(), kernel picks one of the accepting threads/processes and delivers the data to it alone.
See https://lwn.net/Articles/542629/ + my socket book P102.