Research papers in middleware technologies for IoT explore the crucial role of middleware as an intermediate layer that bridges heterogeneous devices, communication protocols, and applications to ensure seamless interaction within the Internet of Things ecosystem. These works analyze how middleware provides core services such as device abstraction, service discovery, interoperability, context awareness, data aggregation, and quality of service (QoS) management. Studies highlight diverse middleware approaches, including service-oriented middleware that enables modular and reusable components, event-driven middleware for real-time responsiveness, agent-based middleware for autonomous decision-making, and cloud–fog–edge middleware for distributed data processing and low-latency services. Semantic middleware solutions are also widely studied for enabling machine-readable metadata, ontologies, and semantic interoperability across diverse IoT platforms. Security-focused middleware architectures are examined for their ability to incorporate authentication, access control, encryption, blockchain-based trust mechanisms, and privacy-preserving data sharing. Advanced works highlight middleware’s role in integrating AI and machine learning for adaptive service orchestration, anomaly detection, predictive analytics, and dynamic resource management. Application-driven studies demonstrate middleware’s importance in domains such as smart healthcare, where it ensures secure and reliable patient monitoring; in smart cities, where it supports large-scale interoperability among urban services; in industrial IoT, where it enables real-time monitoring and automation; and in intelligent transportation, where it manages low-latency communication for safety-critical applications. Collectively, this body of research shows that middleware technologies are indispensable for addressing challenges of heterogeneity, scalability, interoperability, and security, while laying the foundation for next-generation IoT systems that are intelligent, resilient, and adaptive.