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

    Creates a client handle and returns its address. Seeks to use a
    server supporting the highest version number within a specified
    range.
    Format
      #include  <rpc/rpc.h>
      CLIENT  *clnt_create_vers(char *host, u_long prognum, u_long
              *versnum, u_long min_vers, u_long max_vers, char
              *protocol);

1 - Arguments

 host
    A pointer to the name of the remote host.
 prognum
    The program number associated with the remote procedure.
 versnum
    The version number associated with the remote procedure. This
    value is returned by the routine. The value is the highest
    version number supported by the remote server that is in the
    range of version numbers specified by min_vers and max_vers. The
    argument may remain undefined; see additional information in the
    Description section.
 min_vers
    The minimum acceptable version number for the remote procedure.
 max_vers
    The maximum acceptable version number for the remote procedure.
 protocol
    A pointer to a string containing the name of the protocol for
    transmitting and receiving RPC messages. Specify either tcp or
    udp.

2 - Description

    The clnt_create_vers routine creates an RPC client handle
    for prognum. An RPC client handle is a structure containing
    information about the RPC client. The client can use the UDP
    or TCP transport protocol.

    This routine uses the Portmapper. You cannot control the local
    port.

    The default sizes of the send and receive buffers are 8800 bytes
    for the UDP transport, and 4000 bytes for the TCP transport. The
    retry time for the UDP transport is 5 seconds.

    The clnt_create_vers routine differs from the standard clnt_
    create routine in that it seeks out the highest version number
    supported by the server. If the server does not support any
    version numbers within the requested range, the routine returns
    NULL and the versnum variable is undefined.

    The clnt_create_vers routine uses the global variable rpc_
    createerr. rpc_createerr is a structure that contains the most
    recent service creation error. Use rpc_createerr if you want the
    client program to handle the error. The value of rpc_createerr is
    set by any RPC client creation routine that does not succeed.

3 - Return Values

    CLIENT *           Client handle containing the server
                       information.
    NULL               Error occurred while creating the client
                       handle. Usually the error indicates that the
                       server does not support any version numbers
                       within the requested range. Use the clnt_
                       pcreateerror or clnt_spcreateerror routine to
                       obtain diagnostic information.