If you want to read/write simultaneously to/from a named pipe (from different threads),
you have to use Overlapped I/O !
Explanation from the docs for "Nonoverlapped I/O":
It is the responsibility of the application to serialize access to the port correctly.
If one thread is blocked waiting for its I/O operation to complete,
all other threads that subsequently call a communications API will be blocked until the original operation completes.
For instance, if one thread were waiting for a ReadFile function to return,
any other thread that issued a WriteFile function would be blocked.