Under normal conditions, a client that sends an SC_CALLBACK_REG message receives a reply that indicates that the registration succeeded or failed.
However, the server can experience an error condition when a client is registering that prohibits the server from sending an SC_REPLY message to the client. In this case, the registration could either have succeeded before the error condition occurred, could have failed, or could not yet have been processed.
Because the server must function as a failover, or highly available, server in the cluster, this error condition does not mean an end to the service. In fact, the server could soon begin sending events to the newly registered client.
To remedy these conditions, your client should perform the following actions:
Impose an application-level timeout on a registration connection that is waiting for an SC_REPLY message, after which the client needs to retry registering.
Begin listening on its callback IP address and port number for event deliveries before it registers for the event callbacks. The client should wait for a registration confirmation message and for event deliveries in parallel. If the client begins to receive events before the client receives a confirmation message, the client should silently close the registration connection.