As the core layer of the Internet of Things (IoT), middleware bridges the gap between applications and devices to resolve many common IoT issues and enhancing application development. Consequently, developing suitable middleware is the main challenge that covers functionality and required quality to combine heterogeneous hardware and software as the integrated system in the IoT. This survey discusses IoT middleware requirements and challenges, and presents the current state of research in this domain. A technical taxonomy is presented for the IoT middleware according to the abstract and processing approach of data. We focus on discovering similarities and differences by making comparisons and appropriateness studies. Besides, this survey discusses three enabling techniques in detail to present analytically the current research trends on the IoT middleware. In the end, we summarize open issues in IoT middleware. This survey aims to provide guidance for the development and research of middleware in the IoT paradigm.

作为物联网（IoT）的核心层，中间件弥合了应用程序和设备之间的鸿沟，以解决许多常见的IoT问题并增强了应用程序开发。因此，开发合适的中间件是涵盖功能和所需质量的主要挑战，以将异构硬件和软件组合为物联网中的集成系统。该调查讨论了物联网中间件的需求和挑战，并提出了该领域的研究现状。根据数据的抽象和处理方法，针对物联网中间件提出了一种技术分类法。我们专注于通过比较和适当性研究发现相似之处和不同之处。除了，本次调查详细讨论了三种启用技术，以分析方式介绍IoT中间件的当前研究趋势。最后，我们总结了IoT中间件中的未解决问题。该调查旨在为物联网范例中的中间件的开发和研究提供指导。