Performance Evaluation of OPC UA PubSub Implementation for ESP32 Microcontrollers in Local and Cloud Environments

The integration of legacy industrial assets into IIoT frameworks requires standardized protocols compatible with resource-constrained hardware. This paper evaluates an implementation of the OPC UA PubSub protocol (IEC 62541-14) developed in MicroPython for an ESP32 microcontroller, addressing the challenge of deploying industrial communication standards on low-cost embedded platforms. This research benchmarks the protocol stack's performance through systematic 50-sample statistical analysis, comparing local and cloud MQTT broker deployments. The methodology isolates protocol processing overhead from network infrastructure effects, enabling the precise characterization of implementation efficiency. The results demonstrate a deterministic internal serialization time of 8.46 ms (± 1.26 ms), which remains invariant regardless of network infrastructure, validating the protocol's computational stability. The library maintains a minimal memory footprint, with a peak consumption of only 4.86 KB per message cycle. Network performance analysis revealed significant differences between deployment scenarios. Local broker deployment achieved an average RTT of 119.71 ms with a jitter of 111.37 ms, while cloud broker deployment exhibited an RTT of 985.36 ms with a jitter of 206.49 ms. Despite the 8.2× latency increase in cloud scenarios, the system maintained a 100% message delivery success rate without packet loss across all test conditions. This study concludes that this implementation provides a robust foundation for industrial telemetry and monitoring applications in brownfield scenarios, demonstrating resilience under varying network conditions while maintaining strict protocol compliance with IEC 62541-14.