MQTT's single-level wildcards allow you to Subscribe to multiple Topics simultaneously while using a specific Topic structure (they will follow any possible Subscription that would render the same Topic Structure) .

Single-level wildcards are represented with a plus sign (+). For example, if using the following Subscription Topic with a single-level wildcard:

Topic

/v1.6/devices/+/{VARIABLE_LABEL}

Then the response will be updated with the Last Dot of a device which contains a variable with the same {VARIABLE_LABEL} as specified in the Topic and that has received a value.

Examples

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Note

The bash example from this section makes use of the Eclipse Mosquitto library, if you wish to test it please install it using the official instructions.

If there are 3 Devices which contain the following Variables:

Using single-level wildcard Subscription to obtain a value/dot sent to a specified Variable to any Device
When using the following single-level wildcard Subscription Topic:

/v1.6/devices/+/pressure/lv

/v1.6/devices/+/pressure

Then the results would be as if multiple Subscriptions were made as following:

/v1.6/devices/device-a/pressure/lv
/v1.6/devices/device-c/pressure/lv

/v1.6/devices/device-a/pressure
/v1.6/devices/device-c/pressure

Hence, the response would be updated if either device-a or device-c receive a new value/dot for their pressure variable.

$ mosquitto_sub \
-h "industrial.api.ubidots.com" \
-t "/v1.6/devices/+/pressure/lv" \
-u "BBFF-Rfcgaxns6HlVb155WA0RhSY85xNDmB" \
-p 1883 \
-q 1
-v

$ mosquitto_sub \
-h "industrial.api.ubidots.com" \
-t "/v1.6/devices/+/pressure" \
-u "BBFF-Rfcgaxns6HlVb155WA0RhSY85xNDmB" \
-p 1883 \
-q 1
-v

Using single-level wildcard to obtain the last value/dot of any variable from a device when it is updated
Use the following Subscription Topic:

/v1.6/devices/device-a/+/lv

/v1.6/devices/device-a/+

Then the results would be as if multiple Subscriptions were made as following:

/v1.6/devices/device-a/temperature/lv
/v1.6/devices/device-a/pressure/lv
/v1.6/devices/device-a/humidity/lv

/v1.6/devices/device-a/temperature
/v1.6/devices/device-a/pressure
/v1.6/devices/device-a/humidity

Hence, the response would be updated if device-a receives a new value for either its temperature, pressure, or humidity variable.

$ mosquitto_sub \
-h "industrial.api.ubidots.com" \
-t "/v1.6/devices/device-a/+/lv" \
-u "BBFF-Rfcgaxns6HlVb155WA0RhSY85xNDmB" \
-p 1883 \
-q 1
-v

$ mosquitto_sub \
-h "industrial.api.ubidots.com" \
-t "/v1.6/devices/device-a/+" \
-u "BBFF-Rfcgaxns6HlVb155WA0RhSY85xNDmB" \
-p 1883 \
-q 1
-v