Internal work

[MikeTatsky]

May I ask you to write about internal work of socket.io?

I want to know:
1 - Sequence of priority of chosing sending technology.
I think it is follows: Web Socket, Flash Socket, XmlHTTP 2, JsonP, usual Ajax.

2 - Also I very want to undertand socket protocol.
I tried to realize socket server code by myself and come across some protocol sicurity issues.