VMS Help TCPIP Services, Programming Interfaces, Sockets API, getprotobynumber(), Description  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    This function returns a pointer to a protoent structure
    containing the data from the protocols database:
    struct  protoent {
            char   *p_name;       /* official name of protocol */
            char   **p_aliases;   /* alias list */
            long   p_proto;       /* protocol number */
    };
    The members of this structure are:
    p_name             The official name of the protocol.
    p_aliases          A zero-terminated list of alternate names for
                       the protocol.
    p_proto            The protocol number.
    All information is contained in a static area, so it must be
    copied to be saved.
    Related Functions
    See also getprotoent() and getprotobyname().