ipv6 aware application development

[flt...@yahoo.com]

Hi experts,

I know this is a basic question but I can't seem to find a post
that talks about this.

I am trying to write a v6 aware application.
If a hostname resolves to both a v4 and v6 address, how does
my application know whether it should connect with v4 or v6?
First of all the host may or may not have a v4 or v6 address (do
I need to check that first?) and even if it has both v4
and v6 addresses, it may only have a route to the destination
for just one of them...

How does IE do it? In IE I can type in a name that resolves
to both v6 and v4 addresses, and it connects just fine without
me telling it which one to use.

Can someone explain to me if I want to write a v6 aware application
how is it supposed to behave?

Thanks