The subscribers have two components: the Open Subscriber and the Data Stream Handler. The Open Subscriber handles interface issues and queues up messages for the Data Stream Handler, and the Data Stream Handler routes the messages to their final destination.
Each data stream listens for packets on one UDP broadcast channel. When a packet arrives on a channel, the subscriber checks and records the packet sequence number to determine potentially missing packets. The packet recorder has a fixed size window. If the packet recorder is full, the subscriber asks the publisher to resend the missing packet on the publisher resend channel. The packet recorder will then shift its window by one packet.
RAP includes two Data Stream Handlers: the RAPCache Data Stream Handler (Cache DSH) and the RAPStore Data Stream Handler (Store DSH). The Cache DSH loads messages into ASE. The Store DSH loads messages into Sybase IQ. The Demo Subscriber component includes a Demo Data Stream Handler that can be configured to write or discard messages.