Most programs would simply use bind(), instead of having a more complicated option parsing and condition around bind()/bind_unused(): sockaddr_in sockaddr

Most programs would simply use bind(), instead of having a more complicated option parsing and condition around bind()/bind_unused(): sockaddr_in sockaddr = { 0 }; sockaddr.sin_port = HARDCODED_PORT; // other fields defaulted... // option parsing and filling sockaddr structure... if (has_port_number && flag_use_random_port) { error(...); exit(1); } if (has_port_number) { bind(s, sockaddr); } else { bind_unused_port(s, sockaddr); } vs. sockaddr_in sockaddr = { 0 }; sockaddr.sin_port = HARDCODED_PORT; // other fields defaulted... // option parsing and filling sockaddr structure... bind(s, sockaddr); Yeah, people would just write the second version. And mind you, the sockaddr argument for bind_unused() still would have a local address to bind to, so what exactly is gained? Difference between 65535 or 65536 ports available doesn't warrant complicating API in such a manner, IMO.