Im interested about this topic.
I found a bluetooth plugin based on cocos2d-x 3.1.
The readme is in Japanese.
From my research, it seems like for p2p LAN, we would need TCP/IP to handle the communication on the network level. One would need to do a broadcast signal while the rest listen for the broadcast. I believe thats the layman terms to establish a connection within local LAN.
With regards to the technology to use for it, it seems like either SocketIO or Websockets is able. Both are included in Cocos2d-x 3.x.
It seems there are interested parties previously.
Im not sure what the result of it.