Automatic address assignment by the system

You can still call a function for a socket which actually requires a bound socket (e.g. connect(), sendto()), even if the socket has no address assigned to it. In this case, the system executes an implicit bind() call with wildcards for the Internet address and port number, i.e. the socket is bound with INADDR_ANY to all IPv4 addresses and with IN6ADDR_ANY to all IPv6 addresses and IPv4 addresses of the host and receives a free port number from the range of non-privileged port numbers.