One of the challenges for buyers in real estate is knowing the most current listing information. The MLSN Protocol resolves this issue for public access to listing information, but it is based upon a request/response protocol. A user must manually query an mlsn server to find out the latest increase or decrease price for a listing. Whereas, the publish/subscribe could be used to receive listing information automatically over the Internet.
In the diagram above, users subscribe to topic message queues using the PubSubListing Protocol. When a listing's price changes, this update is sent to the messaging server which updates the subscribed topic queues, respectively. The pricing update is broadcasted over the PubSubListing Protocol to the users who then view the new price on their laptop, desktop machine, or mobile device. This broadcast pattern continues whenever the listing's price changes. Users have the ability to continue to receive future broadcasted messages by remaining subscribed or unsubscribing to the topic queues.
In summary, the obvious benefits of the PubSubListing protocol are the automated messages of changes and the ability to subscribe or unsubscribe to topic queues. The next step for the protocol is to apply for a reserved port with IANA.