I used to mimimc the power off scenario using a wired connection and a router. The client machine ethernet connects to an up-linked router, and to mimic the se

I used to mimimc the power off scenario using a wired connection and a router. The client machine ethernet connects to an up-linked router, and to mimic the server's poweroff, we just pull the uplink cable out from the router. As far as the client can tell, the network interface is still up (because the router is still alive). If you pull the client side cable from the router, the client's network stack detects the lost network interface and the socket closes immediately.