Android :: How To Be Notified On Wifi Network Status Change?

I am writing an app that connects to a telnet server via wifi. I have a service that manages the socket connection. It all works fine, but when the phone sleeps it disconnects the wifi radio, which causes the socket connection to break (and throws a SocketException). I feel like I should be able to set up a a broadcast receiver whose onResume() method is called when the wifi network connection is lost, and that would allow me to gracefully shut down the socket, and re-open it if the network is immediately re-connected. But I can't find anything like that in the doc or via searching.