Thanks for the help!
Attempts to ping my Roku's IP address time out, so that's not working. But I *can* navigate to my Roku's IP address with my browser, and installed the client.zip file through the page. (I got a warning that the application exceeds the maximum recommended size but it looks like it installed correctly.)
When I start the server in terminal, I get this:
writing configuration
http://0.0.0.0:8007/The "Stop Server" button is there, but I'm assuming the server isn't running given the 0's in the IP address, and I can't connect to the server IP address using my broswer.
I haven't changed any firewall / router settings, but I do have another server that runs on my computer (I have a Squeezebox for my audio files) and it's possible it's interacting with my firewalls / router settings and mucking things up. Is there somewhere I should check to see what the firewall / router settings are?