Abstract-Cooperation between Wireless Sensor Networks (WSNs) is needed in order to fully realise the vision for the Internet of Things (IoT). As endeavours towards IoT continue, compatibility and interoperability between distinctive networks in WSNs becomes crucial. However, considering the wide range of WSN applications, heterogeneity in the platforms and communication protocols in use is potentially unavoidable. To help integrate WSNs with IoT, this research studies a framework to enable Opportunistic Direct Interconnection (ODI) between distinctive WSNs. The interconnection of different WSNs, using different internal communication protocols, are practically validated with empirical experiments. ODI involves the addition of a lightweight shared protocol for interconnection between WSNs. The implementation confirms the feasibility of ODI as a practically obtainable system, and quantifies the low overheads in terms of memory and energy.