Device support

Unfortunately, this is where we run into problems. Support for Internet-free sharing of data is extremely sparse on mobile platforms. Android supports peer-to-peer Wi-Fi, Near Field Communication (NFC), Bluetooth, and USB. However, this is specific to Android. If you want access to these features on iOS or Windows Phone, you're out of luck. Let's start by inspecting the support provided by Android, then evaluate a couple of libraries that can be used to emulate this functionality on other platforms.

Open http://developer.android.com/guide/topics/connectivity/ in your browser and note the support for the following interfaces.

Bluetooth

Bluetooth is a protocol with a typical range of 10 meters. If you're sharing data with someone in the same room, Bluetooth is a good choice. Let's see what the sharing process looks like:

Bluetooth pairing process

There are a few things that we could do to make this process simpler. First, we could turn on discoverability automatically. Second, we...