Subscribe to channel updates from a particular field of a channel with MQTT
ThingSpeak™ MQTT requires an MQTT API Key to subscribe to channel updates for both private and public channels. Supply any unique user name and your MQTT API Key as a password parameter to the ThingSpeak MQTT broker when connecting. Choose Account > My Profile to see your MQTT API key. ThingSpeak MQTT supports only QoS 0.
channels/
subscribes to updates from a single field of a channel feed. Replace
<channelID>
/subscribe/fields/field<fieldnumber>
<channelID>
with the channel ID and
<fieldnumber>
with the target field number.
Subscribing to a channel feed automatically returns the last entry in the
channel to your subscription. Invalid subscription details such as API Key,
channel number, or MQTT User API Key result in the client being
disconnected.
channels/<channelID>/subscribe/fields/field<fieldnumber>/<apikey>
subscribes to updates to a channel field from a private channel. Replace
<apikey>
with the Read API Key of the
channel.
channels/<channelID>/subscribe/fields/+
subscribes
to updates to all fields of a channel feed from a public channel.
channels/<channelID>/subscribe/fields/+/<apikey>
subscribes
to updates to all fields of a channel feed from a private channel. Replace
<apikey>
with the Read API Key of the
channel.
If a connection is successful, the server responds with the last value in the subscribed channel field.
Each ThingSpeak license type allows different number of MQTT subscriptions and has different restrictions on the number of messages delivered. For more information, see How to Buy and Frequently Asked Questions.
MQTT subscriptions do not report updates to the channel from Bulk Write JSON Data
or Bulk Write
CSV Data
.
ThingSpeak MQTT honors all MQTT disconnect and unsubscribe messages. If you disconnect from the MQTT server, you are automatically unsubscribed from channel updates.
Configure MQTT.fx to subscribe to channel
field updates from the MathWorks® weather station. Field 2 provides the current wind speed. Use
mqtt.thingspeak.com
and port 1883
. Enter a
unique user name and your MQTT API Key as the password.
Use the subscribe format channels/12397/subscribe/fields/field2
. Since the
MathWorks weather station is public, the /<apikey>
is not
needed. This example is shown with the API key included.
Now update the channel, and observe the messages in your client.
To unsubscribe from channel updates, click the Unsubscribe or Disconnect buttons.
Publish to a Channel Feed | Publish to a Channel Field Feed | Subscribe to a Channel Feed