Hi, I searched for related issues but haven't found anything. I am having some trouble with Windows native Unix domain sockets (a recent feature in Windows 10 and 2019 server) and Cygwin. I think I possibly know the cause since I had to investigate a similar looking issue on another platform built on Windows. The problem is that cygwin commands don't seem to recognise native Unix domain sockets correctly. For example, the socket "foo.sock" should have the same ownership and similar permissions to other files in the example below: $ ls -lrt total 2181303 -rw-r--r-- 1 mimcmah None 1259 Sep 23 10:22 test.c -rwxr-xr-x 1 mimcmah None 3680 Sep 23 10:22 test.obj -rwxr-xr-x 1 mimcmah None 121344 Sep 23 10:22 test.exe -rw-r----- 1 Unknown+User Unknown+Group 0 Sep 23 10:23 foo.sock -rw-r--r-- 1 mimcmah None 144356 Sep 23 10:27 check.ot A bigger problem is that foo.sock can't be deleted with the cygwin "rm" command. $ rm -f foo.sock rm: cannot remove 'foo.sock': Permission denied $ chmod 777 foo.sock chmod: changing permissions of 'foo.sock': Permission denied $ cmd /c del foo.sock But, native Windows commands are okay, as the third example shows. I think the problem may relate to the way native Unix domain sockets are implemented in Windows and the resulting special handling required. They are implemented as NTFS reparse points and when opening them with CreateFile, you need to specify the FILE_FLAG_OPEN_REPARSE_POINT flag. Otherwise, you get an ERROR_CANT_ACCESS_FILE. There are other complications unfortunately, which I'd be happy to discuss further. But, to reproduce it, you can compile the attached code snippet which creates foo.sock in the current directory. Obviously, this only works on recent versions of Windows 10 and 2019 server. All the best, Michael McMahon