With the rapid development of Industry 4.0, upgrading traditional control systems to Internet of Things (IoT)-based solutions has become increasingly important. We propose a low-cost remote monitoring and control system that integrates sensing, data acquisition, and control within a unified IoT framework. The system is implemented on a Raspberry Pi platform using the web framework Django and communicates with a programmable logic controller (PLC) via the Modbus transmission control protocol (Modbus TCP) to acquire electrical and environmental sensing data. A web-based human–machine interface developed with HTML5 and JavaScript enables cross-platform remote monitoring, real-time sensing visualization, and control through standard web browsers. The novelty of this work lies in the integration of lightweight web technologies with industrial PLC-based sensing and control, thereby providing a scalable, extensible, and web-native IoT solution that relies on no proprietary software.