In our former work we have given a high-level formal model of a cloud service architecture in terms of a novel formal method approach which combines the advantages of the mathematically well-founded software engineering method called abstract state machines and of the calculus of mobile agents called ambient calculus. This paper presents an extension for this cloud model which enables client-to-client interaction in an almost direct way, so that the involvement of cloud services is transparent to the users. The discussed solution for transparent use of services is a kind of switching service, where registered cloud users communicate with each other, and the only role the cloud plays is to switch resources from one client to another. 459 Bosa K.. An Ambient ASM Model for Client-to-Client Interaction via Cloud Computing.