The integration of different protocols and technologies remain to date one of the main challenges in IoT. The lack of widely accepted standards at the application layer, and the wide deployment basis of a large number of legacy (e.g. Non-IP) technologies further exacerbate this issue. To date, typically integration is solved with ad hoc solutions on a per-connection basis ("N-to-N"). Such approach does not scale, being suitable only for small scenarios with a limited heterogeneity of technologies. More scalable approaches have been proposed, message-based, and built around a publish-subscribe architecture. In this work we summarize an experimental evaluation of such integration approach, based on the implementation of a Smart Office use case. We describe in detail the main integration issues arisen, and how they have been addressed. Our work shows how to integrate in practice in an efficient and scalable manner highly heterogeneous IoT scenarios.