how are connections established?

[Elaine Cheong]

I am trying to find out how Click does the communication between elements
so that I can compare it to a programming model I'm working on (see below
for links).

I have found sample code for elements in which an element's push() method
calls the push() method of its output port.  Where can I find the code (or
section of the runtime system) that connects the output port push() method
with the input port of the connected element?  Does the output port push()
method call the connected element's push() method, or does the output port
push() method call a method on the connected element's input port, which
in turn calls the connected element's push() method?

I am interested in finding out what parts of the code establishes all of
the connections between elements during initialization (userlevel is
fine), and knowing which methods are called when an element is activated
(especially when going through a push or pull connection).

If you could provide any information that would make this clearer for me
(an explanation, or a pointer to files or sections of files that I should
look at), I would very much appreciate it.

Thank you very much.

Sincerely,
Elaine Cheong

=====
References for "TinyGALS: A Programming Model for Event-Driven Embedded
Systems":
http://ptolemy.eecs.berkeley.edu/papers/03/TinyGALS/
http://ptolemy.eecs.berkeley.edu/presentations/03/index.htm