tcp-udp-networking | Source code from my C # networking tutorial series | Learning library

I am trying to write a server in C# for connecting Unity clients following a guy's tutorial. I'll start by saying that I don't know much about networking, as I am trying to learn during the process. When I run the server (on the localhost) it begins to accept tcp clients through an Async callback, and so when I try to connect via browser by doing "http://localhost:port/", the incoming connection describes 3 clients:

my question is: why?? when I connect from unity through a script, the incoming connection is only one: the player, as it should be.

the server code that I am using: https://github.com/tom-weiland/tcp-udp-networking/tree/tutorial-part1/GameServer/GameServer

It would be really appreciated if you could provide an explanation of how the callbacks work, as while debugging it was weird to see that the lines were running multiple times.