ngrok

"Own your data. Host personal cloud services on your own private network. Run webmail, file syncing, and more securely on your hardware with full end-to-end encryption."

If you have a machine on a firewall from which you can ssh out but doesn't allow incoming connections on any port, you can open a web server on port 80 to the other side of the firewall via:

ngrok http 80

The local address:

localhost:80

will be tunneled to an external address of the form:

http://x1y2z3a4b.ngrok.io


https://ngrok.com/