Sometimes you need to test your local server (localhost) from another network. For example, your iPad uses WiFi and your workstation uses Ethernet and they are in different subnetworks.
The solution is to use tunnel service which redirect all requests to external website to your localhost. You can use localtunnel.me – an npm package. It generates web address, e.g. https://gqgh.localtunnel.me, and redirects requests to specified port on localhost.