Through the intermediate service, if no external IP...
Although external default no rights to listen to the port.
mazie.Towne answered on July 8th 19 at 16:56
In a local network, for example, if both computers are connected to the same router, you can do without problems, and nothing of tuning, but one of the browsers should be the TCP server (or a WebSockets server), the simpler "application-to-application" or "app browser".
Brock_Nader answered on July 8th 19 at 16:58
In a typical browser is not possible to create a socket server, only intermediate service. You can use p2p, but it is only in tor and analogues