I want to be able to send files from an iPhone app to a computer. What would be the easiest way of doing this?

I've made simple server client programs before, but in those, the client has always needed to connect to the server before being able to receive messages from it. There is an app for the iPhone called iSimulate, where you put a server on a Mac (the iPhone simulator), and then you use the iSimulate app of an iTouch or iPhone to send touch events to the server. This app does not require you to type in an ip-address. Instead it presents a list of available computers that have this server up and running.

How exactly is this being done? Can a server broadcast a message over a network, w/o anyone being connected to the server? How does that work? How does a client listen for that broadcast?

Here's a video of the app I'm talking about: http://www.youtube.com/watch?v=N3Qpd1ycZh4