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

 addr
    A pointer to a series of bytes in network order specifying the
    address of the host sought.
 len
    The number of bytes in the address pointed to by the addr
    argument.
 type
    The type of address format being sought. Currently, only AF_INET
    is supported.