Subscribers can be configured to receive messages from one or more Publishers.
Publishers send messages over the network through the datastream channels using UDP multicasting. Each datastream channel can be configured to have a multicast address, an IP address of a local network interface and a local port. The subscribers can be configured to receive messages from one or more publishers by listening for messages on the publishers’ datastream channels. Before you install RAP, define the datastream channel ports, multicast IP addresses and local interface addresses that let components send and receive messages. Worksheets have been provided further on in this chapter to assist you with installation planning.
When a publisher sends a message to a multicast group, all subscribing recipients to that host and port receive the message. If a subscriber misses a message published by one of the publishers, the subscriber requests a resend of the message by communicating with the publisher through its resend port. You must define a unique resend port for each publisher.
The figure below shows the FAST Feed Handler and Demo Feed Handler configured with two datastream channels each. The RAPCache subscriber and RAPStore subscriber are configured to listen to both publishers and therefore each subscriber is listening on four datastream channels. The multicast addresses and port configurations of the subscribers’ channels should be identical to the multicast addresses and port configurations of the publishers’ data channels. The local interface address of the publisher/subscriber datastream channels should be the NIC address of the publisher/subscriber servers respectively. The resend port configurations of the subscribers must match the resend port configurations of the respective publishers. The resend IP addresses of the subscribers should be identical to the NIC addresses of the respective publisher servers.
