Cache Server in local mode - connect failed

I am running Unity 5.5.2 Personal (64bit) and trying to get the Cache Server working.
The cache server is running in a command window, no arguments, output claims it is ready:

Cache Server version 5.3
Cache Server on port 8126
Cache Server is ready

But in Unity when I set the cache server mode to Local (Edit → Preferences → Cache Server), I get this error:
Socket: connect failed, error: No connection could be made because the target machine actively refused it.

There is no additional output in the command window.
Does anyone know what the problem is?

I am on a windows machine, and always had the same connection error. Then i tried to put the Server cachefolder on the root of a drive with a folder name without spaces (i.e. D:\cacheserver). Then the error was gone. In first place i thought it was a coincidence. So second time i put a space between the folder name after restart the error came back, removing the space in the name and restarting resolved the problem for me.

so when i looked to the default cache folder, that is in the usersprofile, that one contains space, i think thats why the error is trown. not sure but for me my workaround works. hope someone find it usefull.