Smart Services using Industrial Internet of Things (IIoT) applications are on the rise, but still more often than not, traditional industrial protocols are used to interconnect the entities of the resulting systems. These protocols are mostly not intended for functioning in such a highly interconnected environment and, therefore, often lack even the most fundamental security measures. To address this issue, this paper reasons on the security of a communications protocol, intended for Machine to machine (M2M) communications, namely the Open Platform Communications Unified Architecture (OPC UA) and exemplifies, on a smart energy system, its capability to serve as a secure communications architecture by either itself or in conjunction with traditional protocols.