I got it working. I am not a networking professional, so if you follow these instructions and end up with your camera feed playing on a billboard in times square, it's your own fault.
Some basics about Stunnel, as I know it: Let's say you previously would have used the ip address of 192.168.0.2:8290 to access the
blue iris server internally. With stunnel, you use the ip address of 192.168.0.2:8291, then have stunnel redirect that traffic to 8290. During the redirect process, Stunnel makes the connection secure. This is a lot more simple than it at first seems.
1. Download stunnel. Use this site
https://www.stunnel.org/downloads.html and download the .exe file, if you're using Windows. If you're not using windows, don't follow these instructions.
2. Install stunnel. Keep all the defaults.
3. In your start menu, go to Stunnel>stunnel GUI Start.
4. Click Configuration at the top, then Edit Configuration.
5. Scroll to the bottom. Below "Example SSL client mode services" delete all of the lines that don't start with ;. You don't need these.
6. Insert this text where you just deleted the other code:
[blue-iris]
accept = 8344 *or whatever port you want to have your computer accept TCP
connect = 8347 *or whatever port you specified on the Blue Iris Webserver page at the top
7. Save the file, close it, then go to Configuration back on the GUI and select Reload Configuration. Close the GUI.
8. Start menu > stunnel Service Install
9. Start menu > stunnel Service Start
10. The address you will use to access Blue Iris will now be your IP address followed by :8344, or whatever port you used. On the blue iris app, you will also need to edit the server settings and select Server is HTTPS, or it won't work.
11. You also need to make sure that your router is properly forwarding requests to your computer. So when you type in your external IP followed by :8344, your router knows to forward that traffic to 192.168.0.2:443. Those numbers don't have to be the same. You could have your router accept on port 8342 and forward to port 8344 on your computer, then have stunnel forward traffic from 8344 to 8347 by using accept = 8344 and connect = 8347, then have the blueiris webserver be located at 8347. Using a random port rather than 443 or 80 or 81 is better, or so I've read. If you do this, you will have to use port 8344 for internal connections (over the same wifi) and port 8342 for external connections (from work or over cellular).
12. If you're getting errors, make sure that you've installed the service and then started it. Also make sure your blue iris app is set to use https, and you're using the proper port. The port on the app needs to be looking for the port on the router that will forward to the port on the computer, which will then forward to the port of blue iris. If you put in the port of the blue iris web server, you're going to have a bad time.
