Check if WCF service is unavailable

I am looking for something similar. Excuse me if it is very basic question.

In this question, the given sol开发者_如何学JAVAution says, "if you detect a server disconnect, enter a "Ping" mode" My question is how do we detect server disconnect?

One can detect server disconnect only by calling method, please correct me if I am wrong.

and in any case what is the best way to check if the service is unavailable?

EDIT: If it is duplicate of another question, which has proper solution, please mention the same before voting it to be closed.