Application client. How do they work?

Question

Software design

How do uTorrent, Bitcoin and other client-client applications work?
I don't understand how they communicate with each other.

Answer 1

I don’t know how to explain it correctly, but utorrent works through a server (tracker), the address of which is written in the torrent file itself. There can be several trackers, it is through them that clients are detected by each other, and then a normal connection is established between them, such as a socket or something