They are implememented now as far as I could get. See Bug #57690 

Looking at the code for gnet (http://www.gnetlibrary.org),
it appears that windows uses a function called
ioctlsocket() to set sockets nonblocking. This
is probably the function we need to use in the
socket version of set/get flags. Try and dig around
a little and see if you can find a file version of
this function, too.

Also, a few comments about the current implementation.
The archtecture dependent code doesn't need to set
the IS_*ABLE flags in its return value, as this
is taken care of in generic code in giochannel.c.
It does, however, need to recheck the values of
is_readable and is_writeable whenever get_flags
is called. If set_flags is unimplemented, you need
to give a warning, not just return an error, as
GError is intended to be used only for run time errors.
I'm attaching a sample patch to give you some idea of
what I'm talking about.

Created attachment 910 [details] [review]
sample patch mentioned in discussion

Moving open 2.0.0 Win32 bugs to 2.0.1 milestone.

Moving 2.0.1 Win32 bugs to 2.0.2 milestone.

Fix applied to HEAD. Quite extensive changes. (Unfortunately, missed 
the 2.1.5 release by a little.) Reopen bug if there still are 
problems.