Eva: An Event-Based Framework for Developing Specialized Communication Protocols

This paper presents a framework for the development of higher level communication protocols that provides extra functionalities (e.g. one-to-many ordered delivery, atomic delivery, etc.) not supplied by standard off-the-shelf lower level communication protocols (e.g. the TCP/IP suite of protocols). The framework is based on the event channel abstraction which allows circumventing the main drawbacks of the layered-based approach traditionally used to develop such protocols, whilst at the same time providing a flexible, simple and well structured way to implement them. The event channel service provided by EVA establishes how entities that share the same address space interact. Then, the application designer has the opportunity to define the most appropriate lower level communication protocols that control the way entities that execute within different processes will interact. The framework specifies a way to accommodate these protocols and provides several standard protocol implementations. Further, it is described a development methodology for constructing applications (specialised communication protocols) on top of the framework. In designing the framework, we have followed the approach of using, whenever possible, well established concepts (e.g. event notification service, design patterns, etc.), thus the paper also discusses the utilisation of such concepts in improving both the efficiency and the structuring of the framework and of the applications to be built on top of it.