Hello,
I just wanted to share that we just installed for a customer a MQTT connection. 5 machines - each producing like 30 live values during the process - are sending the process data as well as SET values to a mosquitto broker. The clients MES system is reading them from there and joining them to other contract data.
From my experiance I have to say that I never saw any protocoll that is that easy to handle and understand and flexible.
As we kept data local, security was no issue, but as already mentioned there are ways (TLS, ..) also, when using VPN it should be safe also I think.
The best thing in here was that we used a straight ASCII format for all values , so just like "12.3 V" for a voltage actual value. So, without any problem we could use e.g. MQTT-Spy (freeware) to check the data on the broker, compare it with the data on the MES and helping us to find really fast some small bugs on the other side.
Also that broker thing in the middle is genious. A client is producing data and writing it to the broker, 0 - n clients may or may not read it. It is a perfect Interface between two parties (e.g. customer and machine manufactorer).
BR
BB