While using file libp2p.js you can simulate how to connect to another PC for talking him / her without any intermediate server.
How to execute
$ npm i
$ node libp2p
Above line will create a config file for remaining you PC / Node for next time.
After this command you will enter REPL mode
> addNode("/ip4/x.x.x.x/:port/:peerId")
> peers // returns all peers that you have to connected
> send(peers[0], ["Hello"])
This Hello messgae will recevies on peers -> 0 index PC / Node
Same as run the above command on peers -> 0 index PC / Node then you will receive a message whatever you entered.