Sorashi

Hello, so after tons of debugging, I found out the PlayerEvent.StartTracking event is server-side only. Can anyone confirm this for me? If that's the case, is there any client-sided event that would allow me to detect hostile mobs in player's area, more specifically boss mobs? Or is that considered a cheat? Where could I find this information about events myself? The Forge documentation doesn't list events nor what they do (or am I wrong?). Thanks for help.