VMS Help CC, Socket Routines, getservbyport  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Gets information on the specified port from the network
    services database. It searches the services database until
    a matching port is found or until an EOF is encountered.

    If a non-null protocol name is also supplied, searches must
    also match the protocol.

    Syntax:

      #include <netdb.h>

      struct servent *getservbyport(int port, char *proto);