We consider efficient real-time communication mechanisms for applications in unreliable and partitionable networks, where network partitions can occur unpredictably and nodes can join and leave arbitrarily. Utilizing quorum systems, we present a quorum-based protocol called SOQ to let nodes update and query service information to a selected set of servers (a quorum). Due to the intersection property of quorums, nodes can obtain latest updated information by simply accessing a quorum. To make the protocol adaptive to network partitions, we propose update/query triggering mechanisms to determine when nodes trigger updates/queries. A quorum access strategy for nodes to judiciously select a quorum to access is designed so that the probability that a query returns the latest service information is maximized. We give in-depth analysis of the protocol, including the communication overhead, load and availability relationship of quorum systems and timeliness analysis of distributed application...