R – WCF Server Push connectivity test. Ping()

Using techniques as hinted at in:

http://msdn.microsoft.com/en-us/library/system.servicemodel.servicecontractattribute.callbackcontract.aspx

I am implementing a ServerPush setup for my API to get realtime notifications from a server of events (no polling). Basically, the Server has a RegisterMe() and UnregisterMe() method and the client has a callback method called Announcement(string message) that, through the CallbackContract mechanisms in WCF, the server can call. This seems to work well.

Unfortunately, in this setup, if the Server were to crash or is otherwise unavailable, the Client won't know since it is only listening for messages. Silence on the line could mean no Announcements or it could mean that the server is not available.

Since my goal is to reduce polling rather than immediacy, I don't mind adding a void Ping() method on the Server alongside RegisterMe() and UnregisterMe() that merely exists to test connectivity of to the server. Periodically testing this method would, I believe, ensure that we're still connected (and also that no Announcements have been dropped by the transport, since this is TCP)

But is the Ping() method necessary or is this connectivity test otherwise available as part of WCF by default – like serverProxy.IsStillConnected() or something. As I understand it, the channel's State would only return Faulted or Closed AFTER a failed Ping(), but not instead of it.

2) From a broader perspective, is this callback approach solid? This is not for http or ajax – the number of connected clients will be few (tens of clients, max). Are there serious problems with this approach? As this seems to be a mild risk, how can I limit a slow/malicious client from blocking the server by not processing it's callback queue fast enough? Is there a kind of timeout specific to the callback that I can set without affecting other operations?