Brian,
You're right, the quick fixes I made for CamlTk to run with Tcl/Tk 8.0
will not work on Windows NT. The proper fix would be to use
Tcl_CreateChannelHandler (Tcl_MakeFileChannel (some_descriptor))
where some_descriptor is the file descriptor under Unix, and a HANDLE under
Windows.
Unfortunately, I didn't have time to look into the Windows version of
our libunix library to see what notion of file descriptor/handle we are 
using there, and if it fits our purpose. You might want to check that
with Xavier, who is the main perpetrator of this library.

--f