The concept of software architecture, also said system structure or system configuration is especially important to design complex software systems, providing a model of the large-scale structural properties of systems. Module interconnection languages (MILs) introduced the idea of creating program modules and connecting them to form larger structures. However, MILs do not support the description of important architectural elements. A new class of description languages, referred to as architectural description languages (ADLs), have recently emerged. Most ADLs, however, support only the description of static software architectures and not dynamic or reconfigurable software architectures. A further limitation of current ADLs is that they focus mainly on the formal notation and usually do not offer proof systems and tools to enable designers to formally verify the properties of their designs. We have developed the ZCL framework, which is a formal framework, specified in Z, to describe and reason about dynamic distributed software architectures. In this paper, we use a simple case study - the client-server system - to demonstrate how our formal framework ZCL can be used to specify and verify reconfigurable software architectures.