OPC UA Pub/Sub supports several transports: UDP multicast (lowest latency, machine-to-machine), MQTT (cloud-friendly via broker) and AMQP (enterprise messaging), making it adaptable to a wide range of use cases.

The Pub/Sub model is transport-agnostic. UDP multicast is used for real-time machine-to-machine coordination such as motion control. UDP unicast is used for direct device-to-device delivery. MQTT is used for cloud IoT scenarios with a broker such as AWS IoT Core, HiveMQ or Azure IoT Hub. AMQP is used for enterprise messaging through Solace, RabbitMQ and similar brokers. The transport choice is driven by latency requirements, scalability targets and the existing infrastructure, with MQTT being the de-facto standard for modern cloud-bound IIoT.

Pick the Pub/Sub transport from the consumer side: if the data ultimately lands in a cloud broker, start with MQTT end to end; if it stays inside the cell for motion sync, UDP multicast is the only realistic choice.