Please check out NetStatusImageDisplay page before trying this example.
If you try this example with HD1100 or HD1200, you will detect a physical interruption of network immediately because when this applet (or application) is connected to HD1100 and HD1200, it keeps checking socket connection in specified time period. When connected to 13xx, the applet (or application) checks connection when some data transmission should occur (when a SerialGateButton is added and pressed, when a client tries to connect to this application (server mode), and when you check the connectivity to a specified IP address).