mqtt

The mqtt service fires off a publish on a topic, creating a new connection to the configured broker for each message.

Consider the following configuration snippets:

[config:mqtt]
hostname =  'localhost'
port =  1883
qos =  0
retain =  False
username =  "jane"
password =  "secret"
targets = {
  'o1'    : [ 'out/food' ],
  'o2'    : [ 'out/fruit/{fruit}' ],
  'm2'    : [ 'sometopic',  'specialmq.ini' ],
  }

[in/a1]
targets = mqtt:o1, mqtt:o2
format =  u'Since when does a {fruit} cost {price}?'

The topicmap specifies we should subscribe to in/a1 and republish to two MQTT targets. The second target (mqtt:o2) has a topic branch with a variable in it which is to be interpolated ({fruit}).

These are the results for appropriate publishes:

$ mosquitto_pub -t 'in/a1' -m '{"fruit":"pineapple", "price": 131, "tst" : "1391779336"}'

in/a1 {"fruit":"pineapple", "price": 131, "tst" : "1391779336"}
out/food Since when does a pineapple cost 131?
out/fruit/pineapple Since when does a pineapple cost 131?


$ mosquitto_pub -t 'in/a1' -m 'temperature: 12'

in/a1 temperature: 12
out/food temperature: 12
out/fruit/{fruit} temperature: 12

In the first case, the JSON payload was decoded and the fruit variable could be interpolated into the topic name of the outgoing publish, whereas the latter shows the outgoing topic branch without interpolated values, because they simply didn't exist in the original incoming payload.

In the first case, the JSON payload was decoded and the fruit variable could be interpolated into the topic name of the outgoing publish, whereas the latter shows the outgoing topic branch without interpolated values, because they simply didn't exist in the original incoming payload.

The optional second value in the topic map (specialmq.ini in the example above) specifies the name of an INI-type file with parameters which override the basic configuration of this service. Assume most of your MQTT targets go to localhost, but you want one target to be configured to address a distinct MQTT broker. Create an INI file with any name you desire and specify that as the optional second parameter:

[defaults]
hostname= 10.0.12.1
port= 1884
client_id = blub01
qos = 1
retain = False

[auth]
username = jjolie
password = seecret

[tls]
ca_certs = foobar.crt
;certfile = xxx.crt
;keyfile = xxx.key
tls_version = tlsv1
;ciphers = xxxxx xx

This shows the currently full configuration possible. Global values from the mqtt service override those not specified here. Also, if you don't need authentication (auth) or (tls) you may omit those sections. (The defaults section must exist.)