The inclusion of Internet communication within the loop of control is innovative compared with the design methodologies of classical control system. This paper presents the design and implementation of a web-based, real-time temperature control system using an Internet-based embedded microcontroller. The UML classes are employed to encapsulate the system architecture to be consistent with the modularity configuration of the controller and software engineering design methodologies. By applying standard Internet protocols (HTTP and SMTP), the remote user may monitor system performance and modify control parameters with the general Internet browser. The test results show the promise of Internet-based control systems for many real-world applications such as tele-manufacturing and tele-robotics.