It's the only one I've seen that abides to the bittorrent spec (where possible). BEP 9 and 10 support incoming.
(Demo's broken, need to push a fix :()
Also note that currently DataChannels do not support reliable transfer and have a small MTU, so sending enormous files does not yet work. With PeerJS you can send smaller files, but larger ones will take an unreasonable amount of time.
So what browser API does the PeerJS use to exchange data with something other than a server, particularly another browser?
Is this it? https://tools.ietf.org/html/draft-jesup-rtcweb-data-protocol...
If so, you still need wifi for the connection between them, The cool thing about PeerJS is that the data goes directly between the computers (A <--> B) without a server in between (A <--> S <--> B).
Your browser version: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.43 Safari/537.31
Currently Google Chrome 26.0.1403.0 or above is required.