The full path to trio-applet.htm should be /usr/local/tRio/docs/trio-applet.htm, so I put added root="/usr/local/tRio" to my http-server tag.

Now I get
'Problem processing GET: /docs/trio-applet.htm (No such file or directory)'

With /usr/local/tRio as the root, it seems to me that it should see the file. Any other ideas??