Creates an RPC server handle using the UDP transport, to
    which it returns a pointer. Upon completion, xprt->xp_sock is
    the transport's socket descriptor, and xprt->xp_port is the
    transport's port number. The service is automatically registered
    as a transporter (thereby including its socket in svc_fds such
    that its socket descriptor is included in all RPC select system
    calls).

                                   NOTE
       Since UDP/IP-based ONC RPC messages can only hold up to
       8 KB of encoded data, this transport cannot be used for
       procedures that take large arguments or return huge results.