Connecting the Unity Profiler to a Windows Standalone Player does not work in 5.6.0b3 anymore.
The Profiler window does not show any samples. Closing the Player causes the Editor to output lots of “Sending message header failed” warnings to the Console window. Sometimes the Player also freezes while closing and needs to be terminated via Windows Task Manager.
See Case 867091 for a video demonstration, reproduce steps and project to reproduce the issue.