@LordCaramac @yura @a1ba I think that lends itself more to induced lethal disturbances than optical systems (let's ignore "directed energy weapon" levels of energy, because that's also lethal).

Optical systems don't need to involve a socket. Point-to-point FSO is a thing.

No WiFi or Bluetooth or Jitsi or anything like that, that can be hacked too easily, just some data transfer method that only works over a distance of a few millimetres

WiFi and Bluetooth have issues based both on being disasters on a software level and being largely broadcast-based.

only works over a distance of a few millimetres

That's more of a current-implementation thing than a strict physical limit (ignoring the use of relays to bypass that).

An opaque armband (for example) covering an optical transceiver provides a considerably more reliable way to ensure only a single device is being communicated with directly.