That's definitely a description of GHC Haskell. All network IO in Haskell goes through a subsystem called the IO manager, which makes use of platform appropriat

That's definitely a description of GHC Haskell. All network IO in Haskell goes through a subsystem called the IO manager, which makes use of platform appropriate high-performance non-blocking APIs. (Actually, I think windows isn't getting an IOCP implementation until the next major release, but Windows has always been a bit undersupported by GHC.) The nice thing about this is... You don't have to care. Haskell is a good enough programming language to just put the platform-specific non-blocking hell APIs in a library and let you write code that looks linear and blocking. If you want more control you can get down to the low level non-blocking APIs, but that's usually not going to be worth the trouble.