Extending EventDispatcher with dynamic event types

Question

I'm currently trying to write my own class to extend the
EventDispatcher class. My goal is to create a Service class which
acts as a switchboard for incoming socket data. Incoming socket
data is parsed to create an Event which is Dispatched to the
appropriate Service object which dispatches the event to any
registered listeners.
The problem I'm having is that I'm confused about how to
handle the event types -- the string parameter which is always
supplied as the first argument to the addEventListener() function.
In all the examples I've seen, the value supplied is a class
constant like MouseEvent.CLICK or VideoEvent.READY. In the case of
my application, I want the developer to define their own Event
types without having to go and edit my class files. In other words,
I'd like to use dynamic event types with my class--maybe something
like the code I've attached.
I'm not new to Actionscript but am very new to the
EventDispatcher class. I'm wondering a bit what that first
parameter really does in a strict programming sense -- i haven't
seen it explained all that well in the piles of documentation I've
read on the Adobe site so I don't really know if I need to define
my own Event class or what and whether I have to define all those
possible event type constants/strings in advance or what.
Any help/advice would be much appreciated.

Answer 1

I have looked it up here:
Actionscript
3.0 Language Reference
and it just says that the first arg to 'addEventListener' is
"The type of event" with no further explanation at all.
I have read this:
Flash
Quick Starts: Programming With Actionscript 3.0: Event handling
It doesn't help much either. It tells me I need the
appropriate event object which makes me wonder DO I NEED MY OWN
CLASS? For that first ard to addEventListener, it merely says
"Substitute the appropriate constant". Given that I want to use
dynamic types (i think so anyway) that is not helpful information
either. Every single example on that page uses a class constant for
event type.
It links to
this
which says "First, the name of the specific event you want to
respond to. Once again, each event is affiliated with a specific
class, and that class will have a special value predefined for each
event--sort of like the event's own unique name, which you should
use for the first parameter." Still no useful detail about what
that arg does and the insistence on constants.
The quick start page also has a link title "Handling Events"
in Programming ActionScript 3.0 but it links to some documentation
titled "Working with XML". The only discussion of events in that 10
or so pages is because some user posted a comment.
I have read this
entire
article which is more helpful than anything in the flash docs
but still doesn't answer all my questions which (AGAIN) are:
1) What is the real function of the first argument to
addEventListener? I have not seen a clear explanation anywhere.
2) Do I need to write my own Event class?
3) What about dynamic event types that are defined at
runtime? Are there any pitfalls or risks that arise from using a
string instead of a predefined constant as the first param to
addEventListener() ?
Please stop telling me to read the documentation. I've been
reading it for days.