In most cases, you don't really want a localhosted site to be accessible from outside your machine, but there are certain circumstances where you may need to, if you're a multiple person team, and you're wanting to collaborate on MyRobotLab without sharing the same machine.
Enter Local Tunnel, you can find a copy of the download here: https://github.com/localtunnel/localtunnel
Now instead of placing this folder just anywhere, for simplicity I place it in my MyRobotLab folder. Now go to your command line (I prefer to use Nano, when not using MyRobotLab UI), and type:
PF represents port forward. Once you're on the screen, grab a local copy of the client file for localtunnel and place it in as if you were executing the ./client command followed by the port that belongs to the MyRobotLab gui: that should be -p 8888. You could pick a subdomain if you want, but this will be a temporary website anyway.
Now simply link that temp site to your friend. If security is a concern, use some kind of temporary URL shortener so it can't be opened by someone else.
I still have yet to test to see if this is actually practical, but this is what I do when I want to share files, and I don't have any of my thumb drives on hand.
Additionally, I use Nativefier to build chromium applications, because Linux generally comes with Firefox, and I'd prefer not to download Chrome myself.