Further to my previous posting, it seems that I was wrong. There is
support for an InitialStatePartner in most of the sample code.

What this does is read a saved state file, which is an XML file, from
the store. Unfortunately, the SDK ships without any of these files
and if the service creates one then it writes COM1 (which is the
default) into the config file so it just continues using COM1.

The service probably creates a new saved state file whenever it is
run. (I have not looked in the code you are talking about.) You
need to look in the code to find the filename that is specified in
the InitialStatePartner attribute, then edit the file and change COM1
to something else. If it does not create a state file, add a call to
SaveState(_state) in the code when it has finished initializing.

_state is the name of the service state instance -- you will have to
figure this out from the code too because there does not seem to
be a standard naming convention.

Trevor