protected abstract IAsyncResult OnBeginOfflineAnnouncement (DiscoveryMessageSequence messageSequence, EndpointDiscoveryMetadata endpointDiscoveryMetadata, AsyncCallback callback, Object state); protected abstract IAsyncResult OnBeginOnlineAnnouncement (DiscoveryMessageSequence messageSequence, EndpointDiscoveryMetadata endpointDiscoveryMetadata, AsyncCallback callback, Object state);