All:
Thanks for the helpful hints along the way. I appreciate the high level of interest in the Topic that I created, but (to me) it seems like many of the replies have strayed a bit too far from the intended path.
At this time I cannot highlight any individual reply that would qualify as an "Answer", though a few of them (taken together) seem to form the basis of a solution.
I have just posted a new Topic ('R4 WiFi Mysteries') which is part of my ongoing work on developing this remote, environmental data-logger system. If you look at that new Topic you will see that I am "stuck in the weeds"