On Windows, assuan_sendfd/assuan_recvfd is not supported.
It would be good to support this feature (even if it's not that useful), so that the code base of GnuPG can be more coherent/clean (portability wise), minimizing exceptions.
Lack of UNIX domain socket's FD passing feature, we need to find two solutions for:
(1) Sharing file object (opened by sending end, used by receiving end) between different processes
(2) Multiplexing sending/receiving FD and normal message
- For sharing file HANDLE, we could use DuplicateHandle (possibly by receiving end), by sending end's notifying its HANDLE (and process HANDLE) to receiving end.
- We could use MSG_OOB for the notification of above, for TCP socket.