Mohammed Hlayel, Hairulnizam Mahdin, Mohammad Hayajneh, Heru Nurwarsito
While Industry 4.0 established connectivity and automation as foundations of smart factories, the emerging vision of Industry 5.0 emphasizes human-centric, resilient, and sustainable systems. Within this evolution, integrating Digital Twins (DTs) with Programmable Logic Controllers (PLCs) in cloud environments remains constrained by the lack of communication protocols that satisfy strict real-time requirements. To address this gap, this paper introduces and validates a WebSocket–S7 protocol bridge for low-latency, full-duplex communication between Siemens S7 PLCs and cloud-hosted DT models. The main contribution of this work is the design and experimental validation of a lightweight, event-driven WebSocket–S7 architecture. This architecture decouples real-time PLC execution from cloud-based digital twin interaction, enabling deterministic performance over wide-area networks without relying on brokers or polling mechanisms. A comprehensive evaluation compares the proposed bridge with MQTT, OPC UA, and Modbus for real-time PLC–DT interactions managed through Node-RED. Using AWS as the cloud backend, the study assesses performance, scalability, and stability under single-user and multi-user emulated loads. Protocols were profiled using JMeter (load and latency), Wireshark (packet traces), and the Unity Profiler (CPU/memory on Android), with timing judged against IEC 61588 (≤ 100 ms). In remote cloud deployment, WebSocket–S7 achieved an average round-trip time (RTT) of 87 ms, remaining within the IEC 61588 threshold. It outperformed alternative protocols by clear margins—34.6% lower RTT than MQTT (133 ms), 46.3% lower than OPC UA (162 ms), and 55.2% lower than Modbus (194 ms), yielding absolute gains of 46, 75, and 107 ms, respectively. Under multi-user emulation, WebSocket–S7 maintained sub-100 ms average response times for up to 40 concurrent users with near-zero error rates, while MQTT offered a balanced option for moderate-throughput scenarios. These trends reflect WebSocket’s lightweight framing and persistent, broker-less transport. Together, these characteristics minimize connection overhead and jitter in WAN conditions. The findings position WebSocket–S7 as a lightweight and scalable solution for remote DT–PLC integration, particularly when standardized protocols incur higher overhead. By consistently meeting IEC-compliant timing requirements, the proposed bridge provides a practical and robust foundation for deploying real-time digital twins in both educational and industrial automation settings. © 2026 Hlayel et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Fatima College of Health Sciences, Institute of Applied Technology, Abu Dhabi, United Arab Emirates; Faculty of Computer Science and Information Technology, Universiti Tun Hussein Onn Malaysia, Johor, Parit Raja, Malaysia; Faculty of Computer Science, University of Brawijaya, Malang, Indonesia; College of Information Technology, United Arab Emirates University, Al-Ain, Abu Dhabi, United Arab Emirates
