Abstract Internet of Things (IoT) paradigm connects physical world and cyberspace via physical objects and facilitate the development of smart applications and infrastructures. A physical object is the basic constituent of IoT, often called as smart object, that interact with other objects and possess the information processing abilities. The smart objects when deployed in the real world, collect information from the surrounding environment and this is abstracted as a service. IoT has established a universe where humans are provided smart data services by the fusion of physical objects and information networks. This approach has been extended to include social networking aspects in the IoT that autonomously build social relationships to discover objects and their services viz; Social Internet of Things (SIoT). SIoT enhances information sharing, supports new applications and provide a reliable and trustworthy networking solutions utilizing the social network of friend objects. In this paper, we present the fundamentals of SIoT, identify thrust areas of it (as service discovery and composition, network navigability, relationship management, and trustworthiness management) and present several prerequisites, challenges and use case scenarios based on them. State-of-the-art research publications are reviewed on service discovery, relationship management, service composition and trust management constituents of the SIoT environment. Finally, we identify and discuss the future research directions that serves as a reference for the next generation discovery techniques to improve service provisioning, find the optimal solution for the link selection in the SIoT structure, develop large scale platforms and provide a smart mechanism for trust evaluation.