Relax. I was providing a reference to the other thread for context since they seem to be the same discussion, and it wastes time for people to be answering questions to two different threads on the (more or less) same subject without knowing the whole story.
Trying to detect "something" coming into the ethernet port is too vague of a question. Any computer connected to a network will always have something coming into the ethernet port. I doubt very much whether you want to be analyzing every single packet that comes in to determine that you've had a file uploaded. Unless the other computer can send you a message I would suggest simply monitoring the directory to look for changes in the list of files like I suggested. In Windows there's an API function that you can hook into that will provide notification of a file system change. There may be something like that for a Mac, but I ain't got a Mac so I can't say what that is.
