Industrial MQTT Gateway

MQTT protocol is event driven and has a Broker/Server to act as middlemen in all transactions. So the traditional read/write transaction doesn’t apply directly, but can briefly associated. For read operation of device, the site will have to publish its tag to the broker when its data is updated. And then the SCADA shall be configured as subscribe from the broker to get notified. Conversely for write operation, the SCADA shall publish any write request (from operator) to the broker, and then the gateway will subscribe to the broker to perform the write operation. So you can see that both pub and sub are involved in both read or write operation.