I think this is the regression just because I've never face such situation before.

Steps:
1. Open Unity Editor on Mac (I used 10.9.4)
2. Run Cache Server on that Mac.
3. Open Unity Editor on Windows (I used 8.1)
4. Go to Preferences -> Chache Server
5. Enter IP of Mac machine where Cache Server is running
6. Press "Check Connection"
==>
"Connection failed"

It works vice versa (Cache Server is on Win and you connect to it from Mac) but also is not stable: connected only if I run cache server on both machine.. then extra server can be shut down.
Cannot identify all the critical conditions for that case.