2 processes can listen on the same port. They would both be calling accept and only one would get accept returned with the first client.

You can open the port, spawn 100 children and have them accept(socket) all at the same time, and they will be receiving equally the new connections, one each, never the same obviously.

If you want to do it from non-related processes, the SO_REUSEPORT flag allows multiple processes to bind to the same address provided all of them use the SO_REUSEPORT option.