Socket being used by another App

[JiminSA]

Hi! I occasionally get a hiccup which I get over by uninstalling and reinstalling xaamp. Apache fails to start with a -1 error code. It appears that another App on my system is hogging xaamp's socket(s) My question is how do I discover the App in question? This I need to know because I shall uninstall that App in favour of xaamp which is my bread & butter (I do web design and development.)