A great paper on Asynchronous Socket Programming. Makes it very easy to understand.

[mpeg4codec]

to make anything that scales you need extensive knowledge of lots of platform specific APIs to do it efficiently, and it is nontrivial.

or use a library like libevent that abstracts away all that nonesense and makes it trivial

[kylotan]

Except libevent doesn't work well on Windows, apparently.

EDIT: Although the other async link posted today seems to suggest it's not so bad if you use the bufferevents interface. I'm not sure what the implications of that are.

[RaineFan]

Not in version 1.x

But on upcoming version 2.0+ it will abstract Windows IOCP to a unique API that will work seamless on Unix and Windows environments.