  The blockchain technology is taking the world by storm. Blockchain with its
decentralized, transparent and secure nature has emerged as a disruptive
technology for the next generation of numerous industrial applications. One of
them is Cloud of Things enabled by the combination of cloud computing and
Internet of Things. In this context, blockchain provides innovative solutions
to address challenges in Cloud of Things in terms of decentralization, data
privacy and network security, while Cloud of Things offer elasticity and
scalability functionalities to improve the efficiency of blockchain operations.
Therefore, a novel paradigm of blockchain and Cloud of Things integration,
called BCoT, has been widely regarded as a promising enabler for a wide range
of application scenarios. In this paper, we present a state-of-the-art review
on the BCoT integration to provide general readers with an overview of the BCoT
in various aspects, including background knowledge, motivation, and integrated
architecture. Particularly, we also provide an in-depth survey of BCoT
applications in different use-case domains such as smart healthcare, smart
city, smart transportation and smart industry. Then, we review the recent BCoT
developments with the emerging blockchain and cloud platforms, services, and
research projects. Finally, some important research challenges and future
directions are highlighted to spur further research in this promising area.
