Resolution:
Three attributes -- network, service, and daemon are
required (there are additonal mandatory attributes that we
won't discuss here) to establish a session (RV or RVCM).
Unless overridden by a user, these attributes assume default
values. The session attributes are described at length in
the TIB/Adapter SDK Configuration and Administrator’s Guide.

The TIB/Adapter for R/3 Configuration GUI provided with
release 3.x does not provide the ability to change session
attributes. You have to use the TIB/Repository Editor to
modify them.
If you want to specify a non-default value for an RVCM
service port while accepting default values for network and
daemon, the following figure shows the TIB/Repository Editor
window, after the service attribute has been changed to the
non-default value of 7501: