HIERARCHICAL PUBLISH/SUBSCRIBE SYSTEM PERFORMED BY MULTIPLE CENTRAL RELAYS

A method for transmitting messages in a publish/subscribe message system. The method also includes: receiving, at a first relay, a subscription request from a first client; recording, at the first relay, subscription information of the first client based on the subscription request; receiving, at the first relay, a publication request from a second client, wherein the publication request includes a message; and transmitting the message to the first client.