Command and Control computing systems are being compelled by market forces to migrate from embedded military computing plants into new baselines of commercial computing technologies. This paper discusses communication middleware requirements that enable cost effective development of complex applications that comprise such systems. For seven years, the High Performance Distributed Computing project (HiPer-D) has developed and instrumented large scale prototype implementations of critical real-time aspects of this computing class for the U.S. Navy using commercial workstations and communication middleware based on the Isis Software Developer Kit.Lessons learned from the continuing development of HiPer-D shipboard prototype applications using various distributed programming methods has yielded a suite of functional requirements that provide the key enabling middleware characteristics described in this paper. Identification of this demanding combination of requirements forms a basis for product evaluation and selection to fulfill some or all of the middleware needs for Command and Control and other shipboard systems. These criteria will be used to support product selections for future HiPer-D implementations and to mitigate the development risk of middleware in Command and Control systems in general.