Imagine a cell phone connected to internet via 3G/4G/5G, but not via wifi (and a router). Wifi is either temporarily disabled on the cell phone, or not available at that area.
Can that cell phone run (for instance) an FTP server that listens on port 2121? Is that something that usual telephony networks allow you to do, on your cell phone, or is that very rare?
I would like to access files on the cell phone with an FTP client located on any other device in the world. I know that, when the cell phone is not connected to a router via wifi, its IP is (usually) dynamic, and changes every time the phone/communication is restarted. Let's assume that that would not be a problem for me. I would just manually find out what is the IP dynamically assigned to the cell phone, and I would "type" that IP into the FTP client.
I have tried all that, with no luck. It looks like telephony networks don't allow TCP/IP connections "towards" specific inbound ports on a cell phone. Internet providers via fiber optic/ADSL/cable do allow those connections (I can, of course, set up an FTP server on my desktop PC behind a router), but it looks like telephony networks don't allow that. Is that right? If so, is there a solution to that? Are telephony networks that allow that common?