Li-Fi is one attempt https://en.wikipedia.org/wiki/Li-Fi

Most of it is, yeah? Fiber-optic cables transmit via laser beams.

Actually p2p file transfer via an infrared port[1] was a fairly common feature on laptops back in the day (this was probably before bluetooth took off). If you're on Windows, have a look in the "Network and Internet" section of the Control Panel. You may still have an Infrared utility there if your computer has that functionality.

[1] https://msdn.microsoft.com/en-us/library/aa940293(v=winembed...

IR was also used for syncing with phones, and printing. Some PDAs (I'm looking at you psion) could print over IR

Back in the day. i used an Orange contract nokia 8310 ir modem and the free phone 0800 number that came with BT internet to give my laptop intenet.

Lasted around 6 months of near 24/7 use before Orange started detecting data and charging contract customers to call 0800 numbers.

I seem to remember the protocol was IrDA, it never worked very well for me.

Data transfer over QR codes http://stephendnicholas.com/posts/quicker-video-qr-codes

See also this post: https://news.ycombinator.com/item?id=12166332#12170616

Link reproduced for clarity:

[1] http://thruglassxfer.com/

[2] Demo of above: https://www.youtube.com/watch?v=2_8GlFdlb0Y

[3] Same idea, some hackable code: https://github.com/Neohapsis/QRCode-Video-Data-Exfiltration

You can probably use a phone's flash and camera for bidirectional data communication with another phone some distance away.