How to make a direct connection between two hosts without opening ports?

Question

C++ / C#

To transfer data in pieces, or to make a stream (audio, video, or just some other data). I'm interested in keywords, for example, by which I could understand how to use it. Or links
I didn’t know which tag to put in, but the one that is suggests what language I’m going to do it in

Answer 1

Without opening ports - in any way (only if in the aisles of one machine).
ps For the sake of curiosity, what did the ports not please?