hi,

You know I want to use that overlapped IO....and have written the whole sing for that
It would make me cry to throw all of it away

Ok, but what is the practical reason of doing that? You can use asynchronous communication instead - no blocking, no problems.
I think i am using asynchronous comm. with a little break :-)
Ok maybe I misunderstood sth. How should I inform my thread that there is data? (without using WaitforMultipleObjects)

I have to react when an event arrives, so I can read from the port.
Is there another way without WaitFor.......?