kqueue API: Filter types

EVFILT_READ
Sockets: listen passed return when connection pending
'normal' return when data can be read (takes SO_RCVLOWAT or NOTE_LOWAT into account)
might return EV_EOF even if there is still data!
Vnode: return when current offset - eof offset is non zero data contains this nonzero value (might be negative!)
Fifos/pipes: return when data can be read. Sets EV_EOF when last writer disconnects. This EV_EOF can be cleared with EV_CLEAR in order to wait for a new writer.

EVFILT_READ