TLDR: Multiple processes can bind to the same port using SO_REUSEPORT flag.

int sfd = socket(domain, socktype, 0);

int optval = 1;
setsockopt(sfd, SOL_SOCKET, SO_REUSEPORT, &optval, sizeof(optval));

bind(sfd, (struct sockaddr *) &addr, addrlen);

As of Linux 3.9 (might have changed a lot since), the requests are distributed evenly using a hash of the connection tuple (sip, sport, dip, dport). It can be quite unbalanced depending on the type of load and has the caveat that the connection might change destination when starting or stopping processes. It might be fixed today using a lookup table.

The Dark Arts of Advanced and Unsafe Rust Programming

Incredible talk about the Apollo Guidance Computer, it goes in such detail in just an hour. The speakers talk fast, but the slides are superb to help follow along. Blown out by this presentation!