This paper focuses on the concept of Digital Twins and a Digital Twin based case study. The first part of the paper provides a discussion on digital twins and categorizations thereof, based on their role in specific applications, the directionality of communication in which they are involved, and levels of integration based on this communication. The second part of the paper outlines a case study of a digital twin with bi-directional communication based on a near-real-time standard protocol involing real interventions in a physical system. The system underlying the case study was developed at Széchenyi István University in Györ, Hungary.