How to connect to a sub-net device from internet? Is it possible?

Question

Example

I mean the situation when you have web-host on your (sub-net cellular internet android device) and try to reach it from your (IP static broad-bond internet laptop)

Problem

As we all know a cellular network is sub-net and has internal IP mask types like 10.0.0.1 and so if you try connect to devices on it, you must be in its local-net. In this case it is that same cellular corporation network, and if you even have that selected device external internet IP, yet thousands of devices synchronously supported by that one same IP, because the whole corporation internal network has one external IP, so you can't directly find and reach to selected device.

Contrary Problem

But if it's that hard, then why you can even make requests on internet and have working services like http, or have instant messaging on your Android device? That proves you'll get instant answers from the out-sided hosts right after you ask something, that means there is no flag determining system that continuously check you in some queue, and alert you to collect your host-sent answers, indeed you have real direct mutual link between you and out-sided hosts.

My Weak Answer

By every request you'll make to internet, your net router stamps your internal IP on header of its own-self external IP, so the called host have your both networks external internetal IP and your device's internal sub-netal IP. In order to allow direct access, so to have a direct link between you and the out-sided host, you have to make the request first to define your complete external internal IP to that host.

Real Problem Is

How do I address that device in my laptop internet browser? Is that like this ===> 233.186.15.78:10.0.2.6:80?

Answer 1

You are never going to be able to route private addresses on the public Internet. When you write, "the cellular network is sub-net and have internal ip mask types like 10.0.0.1," I think you mean that the mobile carriers use NAT to give clients private addresses, which cannot be routed on the public Internet, and must be translated to public addresses as they pass through the carrier's NAT router. The problem is that the translation forces the translated client to initiate since the public address is shared among many carrier clients.

IP packet headers only have two address fields, source and destination, so there is no native IP solution to your problem. Fortunately, there is a solution to your problem which is not too far off from you idea. It is called tunneling. Tunneling encapsulates an IP packet within another IP packet. When the packet address is translated by the carrier NAT router, it is only the outer packet address which is changed. This presents some other challenges, too, since the native addressing on the networks at each end of the tunnel could be the same private networks, but there are ways around that, too.

There are many tunnel solutions, and what you most commonly find is called VPN (Virtual Private Network). There are VPN solutions for mobile phones and PCs. Some are just software on the host, some are on the edge routers, some use Internet servers, and some are combinations of any of the above.