Have you ever tried to quit iTunes and gotten the warning message: "others are connected to your iTunes library...", going on to say that quitting will disconnect whoever it is using your media? If you're like me and have a house full of Apple gear using HomeSharing, you never know which AppleTV is streaming a movie or who's iPhone is jamming to one of your playlists. Common courtesy dictates at least checking what's going on. There are a couple of ways to do this. One is screaming at the top of your lungs, "WHO'S STREAMING FROM MY IMAC??!!!" The other is much more civil and certainly less invasive to your neighbors...
lsof |grep iTunes |grep TCP
iTunes 8258 joe 23u IPv4 0xd862114a55e74e55 0t0 TCP *:daap (LISTEN)iTunes 8258 joe 24u IPv6 0xd862114a3499b6e5 0t0 TCP *:daap (LISTEN)iTunes 8258 joe 49u IPv4 0xd862114a4fa01cc5 0t0 TCP 192.168.1.114:daap->192.168.1.107:62788 (ESTABLISHED)