Setting "Sync Protocol Listen Addresses" and "Global Discovery
Server" in the Settings dialog does not work. This bug seems to
have been introduced in 26d52be.
We need an explicit chmod() when creating a new directory.
Otherwise a new directory may be created with a different permission
from the one received from an originating device, because the umask
is applied to the mode given to mkdir().
The incorrect permission is later sent back to the originating device
and the original permission will be lost.
There is no user/group/others in Windows' read-only attribute,
and all "w" bits are set in os.FileInfo if the file is not read-only.
Do not send these group/others-writable bits to other devices
in order to avoid unexpected world-writable files on other platforms.
