OSF DCE Application Development Guide--Introduction and Style Guide

OSF DCE Application Development Guide—Introduction and Style Guide

1.6.1 Importing the Binding Information from the Namespace

The ﬁrst important thing that the client does is to acquire a binding to the server it wants

to request services from. From the client’s point of view, there are several binding

choices to be made.

The ﬁrst choice is in regard to the binding method to be used; however, this is

determined and implemented as part of the development coding process (the .acf ﬁle).

The binding method chosen has an effect both on what the client has to do in the present

step to acquire bindings, and subsequently on what it must do to maintain them. In this

step, it will be assumed that either the explicit or implicit method was chosen. If auto-

binding were chosen, there would be no need for a discussion, since the client would

then have nothing to do.

1.6.1.1 Getting a Handle

The second choice involves how to get a binding handle. Again, this is a choice that is at

least partially dependent on decisions already made. The client can always generate a

binding handle for itself; the problem is where to get the information that belongs in it.

There are two general solutions, as follows:

• The client imports from the namespace binding handles that already contain the

necessary information, or

• The client receives the information in string form from user input, from a ﬁle, from

another server, or from any other source. It then converts the string into a binding by

calling rpc_binding_from_string_binding( ).

The normal way for a server to make its location known to clients is to export its binding

information into the namespace. The client can then call the following RPC name

service library routines to import one or more bindings from the speciﬁed namespace

entry:

rpc_ns_binding_import_begin(entry_name_syntax, entry_name, if_handle,\

obj_uuid, &import_context, &status);

rpc_ns_binding_import_next(import_context, &binding_handle, &status);

rpc_ns_binding_import_done(import_context, &status);

The name service sees to it that only compatible bindings exported under the speciﬁed

interface, with the optionally speciﬁed object UUID, will be returned to the client. (Note

that the interface speciﬁcation is not contained in the binding, although it is exported to

the namespace entry where it is used by the name service for matching entries to

prospective importers.) The object UUID speciﬁed by obj_uuid is contained in the

binding, if it is present. This is the object UUID that was (optionally) registered under a

type UUID in an earlier step. Even if obj_uuid is not speciﬁed in the import call, it will

be returned in the binding handle(s) if it was exported by the server.

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