This function returns the current name for the specified socket
    descriptor. The name is in a format specific to the address
    family assigned to the socket (AF_INET, or AF_INET6 with BSD
    4.4 when _SOCKADDR_LEN is defined).
    The bind() function, not the getsockname()  function, makes the
    association of the name to the socket.
    Related Functions
    See also bind() and socket().