One of the primary challenges in adopting Industry 4.0 and achieving effective digital transformation is interoperability. With various communication protocols designed to align with different architectures, selecting the right solution becomes crucial for seamless integration and data exchange. RAMI 4.0 is one the most explored and used RA for I4.0. It suggests OPC UA as the preferred solution for the communication layer and an important standard for the information layer. MQTT, integrated in an UNS architecture, has been gaining attention in recent years but there is still no understanding how it can be integrated in RAMI 4.0, more particular in the communication layer. This study concludes about it, starting from technical comparative studies with OPC UA. Preliminary conclusions states that MQTT complies with the technical requirements of the communication layer, and the UNS gives it the structure to be an important solution for the communication and information layer.