VMS Help TCPIP Services, Programming Interfaces, RPC XDR Routines, xdrrec_create, Arguments  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 xdrs
    A pointer to the XDR stream handle being created. The routine
    xdrrec_create fills in xdrs with encoding and decoding
    information.
 sendsize
    The send buffer size.
 recvsize
    The receive buffer size.
 tcp_handle
    A pointer to an opaque handle that is passed as the first
    parameter to the procedures (*readit)() and (*writeit)().
 (*readit)()
    Read procedure that takes the opaque handle tcp_handle. The
    routine must use the following format:
    int readit(char *tcp_handle, char *buffer, u_long len)
    where tcp_handle is the client or server handle, buffer is the
    buffer to fill, and len is the number of bytes to read. The
    readit routine should return either the number of bytes read
    or the value -1 if an error occurs.
 (*writeit)()
    Write procedure that takes the opaque handle tcp_handle. The
    routine must use the following format:
    int writeit(char *tcp_handle, char *buffer, u_long len)
    where tcp_handle is the client or server handle, buffer is the
    buffer to write, and len is the number of bytes to write. The
    readit routine should return either the number of bytes written
    or the value -1 if an error occurs.