More fundamental than the "do they use websockets" question is "what is the multihoming behavior of iOS?"
Sockets alone are not enough -- you need cooperation from the OS to route connections over both wifi and cell data links in the desired fashion.
In this case we can infer it's two connections made by a script running on a web page: one with the "tethered" machine (over wifi) and one with Tether's proxy server (over cell data). The proxy server works in concert with a client on the tethered machine, and the script just relays data between those two connections.
The interesting thing is that iOS permits a single web page to connect over both network links simultaneously. I'm no expert but that seems like something Apple could, and would, kill with an update.
Sockets alone are not enough -- you need cooperation from the OS to route connections over both wifi and cell data links in the desired fashion.
In this case we can infer it's two connections made by a script running on a web page: one with the "tethered" machine (over wifi) and one with Tether's proxy server (over cell data). The proxy server works in concert with a client on the tethered machine, and the script just relays data between those two connections.
The interesting thing is that iOS permits a single web page to connect over both network links simultaneously. I'm no expert but that seems like something Apple could, and would, kill with an update.
Really clever hack, though.