Searches the hosts database that is referenced by the TCPIP$HOST
    logical name for a host record with a given IPv4 address. If the
    host record is not found there, the function may also invoke the
    BIND resolver to query the appropriate name server.
    The $QIO equivalent is the IO$_ACPCONTROL function with the
    INETACP_FUNC$C_GETHOSTBYADDR subfunction code.
    Format
      #include  <netdb.h>
      struct hostent *gethostbyaddr  ( const void *addr, size_t len,
                                     int type );