Table 2.
Overview of application protocols for IIoT devices.
| Level | Protocol Type | Communication Type |
|---|---|---|
| HTTP | Request/response | Asynchronous |
| MQTT | Publish/subscribe | Synchronous |
| OPC UA | Publish/subscribe | Synchronous |
| AMQP | Publish/subscribe | Synchronous |
| CoAP | Publish/subscribe | Asynchronous |
| DDS | Publish/subscribe | Asynchronous |
| Web Sockets | Bi-directional | Asynchronous |
| S7comm | Bi-directional | Asynchronous |
| MOD BUS | Bus bi-directional | Asynchronous |
| PROFINET | Isochronous real time | Isochronous |
| PROFIBUS | Bus Isochronous real time | Isochronous |