How to connect asynchronously (non block) with kqueue?

[zhmt via Digitalmars-d-learn]

I am using kqueue on macosx, I know how to write a simple server. 
But don't know which event will be triggered in kqueue when 
connected successfully , which event when failed?

EVFILT_READ or EVFILT_WRITE?
I have googled this question, got no examples, any suggestions 
are welcome, Thanks.