MQTT topics creates loop with Serial Port

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Hello,
I have question regarding how to deal with MQTT topics.

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I have the following flow that I use to control a sensirion MFC5500. The flow works well without bug. The one problem that I have is when I want to do read the sensor value, I inadvertently created an endless loop.
I trigger a measurement by sending a payload ( "-") on the topic mfc/A01/read. The sensor returns its value as a new payload on the same topic; which starts an infinite loop. In itself it is not the worst unforeseen issue since I need to get measurement at regular intervals, but I would rather have a little bit more control as to when those happen.

What would be the best practice to deal with a situation like this? Is it to check the type of payload (ex. string vs. number) and ignore messages that are not the right type? Is it to create a different topic for the sensor data in a separate branch?

In this specific instance I have multiple type of sensors and it is convenient for me to segregate them by type (ex. mfc, temp, pressure, etc..) and then using a different topic to identify the specific sensor (ex. A01, H03, etc...).

I know their might not be one right solution, I am just curious what the hive mind thinks.
Thank you in advance.
W.

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Personally I would arrange for requests sent to the sensor device to have a different topic from replies. For example mfc/A01/read and mfc/A01/reply.
Then your mqtt-in node could subscribe to mfc/+/reply (/+/ means any single word in the topic, thus it matches mfc/A01/reply and mfc/H03/reply, etc).

Failing that, put a switch node after your mqtt-in to discard those messages where msg.payload === "-"

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