A client interface to the Portmapper, which instructs the
    Portmapper on the host at the Internet address *addr to make
    a call on your behalf to a procedure on that host. Use this
    procedure for a ping operation and nothing else. You can use
    the clnt_perrno routine to print any error message.

                                   NOTE
       If the requested procedure is not registered with the remote
       Portmapper, the remote Portmapper does not reply to the
       request. The call to pmap_rmtcall will eventually time out.
       The pmap_rmtcall does not perform authentication.