Industrial applications based on Wireless Sensor Networks (WSNs) have three main desirable requirements, i.e. low end-to-end latency, low packet loss and low power consumption. Such parameters depend on the network topology as well as on the protocol used to collect data. In the case of WSNs for server monitoring in large data centers, a modular cluster-tree topology is the preferable solution due to the intrinsically clustered nature of this application. However, choosing the most efficient and reliable data collection protocol is not an easy task. In this paper, three protocols for WSNs (i.e. CTP, MultiHopLQI and BLIP 6LowPAN) are experimentally compared with the purpose to assess the performances in terms of latency and packet loss. The obtained results, although preliminary, represent a good starting point to determine the best protocol for WSNs wiwith a modular cluster-tree topology.