A smart gateway, which plays an important role in a smart home, generally connects the internal and external networks of the home, and also jointly manages the smart Internet of Things (IoT) devices equipped with the smart home. Protocols collect generated data from nearby devices and even perform some local data processing tasks. In this paper, we first review the entire research field of smart homes, focusing on a framework based on edge computing and multiple intelligent agents. Then, we divide the evolution of smart gates into three generations based on the timeline and various criteria including quality of experience (QoE), AI support, software-defined networking, etc. Next, we will discuss the key technologies and components of smart gateways such as operating systems, wireless communication protocols, and security. Finally, we examine the challenges and trends of smart gates. This article examines the importance of building a secure smart home system.