Evox, Avalaunch, and several other apps/dashboards run an ftp server.
To get to it from the internet you would have to enable port-forwarding on your router. Users would use your router's server side address for an ip, and the router needs to be told to forward all signals on port 21 to your xbox's ip address. I'm not sure if it's possible without a router, and I'm not sure you really want to either. There are no security settings other than username and password, so you couldn't restrict what people have access to once logged into your xbox. Every user that logs in would be able to delete or rename any of your files, and also it would only work if you're not using the xbox. Running an app or a game shuts down the dashboard, and the ftp server with it.
If you're dying to share some files, either find some http server space to host your files, or find an ftp server for your pc.