Corda - How to check if counter party nodes are running

Question

I have build a CorDapp using "Yo!CorDapp" example (https://github.com/corda/spring-observable-stream), over release-v1 of Corda platform.

The CorDapp has four nodes - Controller node (provides network map service and validating notary service), "node A", "node B" and "node C". Following are the flows defined in the app -

Flow 1: "Node A" sends a trade request to "Node B". "Node C" is also notified.

Flow 2: "Node B" approves the trade request, self-signs it, gets signature from A and closes the trade. "Node C" is also notified.

I want "Node A" to check whether "Node B" is running, so that it can decide to initiate the flow "Flow 1".

Is this possible? If yes, kindly elaborate.