ianmtaylor1 / json_mqtt_pub

Read JSON objects from stdin and publish them to MQTT

json_mqtt_pub

Read JSON objects from stdin and publish them to MQTT.

Publishing topics

This program can use the values of specific keys in JSON objects to determine the MQTT topic it will publish to. If run with,

json_mqtt_pub --topic-prefix home/jsonstuff --topic-keys model id name --topic-suffix value

then the messages will be published to home/jsonstuff[/model][/id][/name]/value, where the model, id, and name in the JSON object are filled in. For example, with the parameters above,

• JSON: {'model':'Acme Corp', 'id':31415, 'name':'Combobulator', 'reading':2.71828}
• Topic: home/jsonstuff/Acme_Corp/31415/Combobulator/value

The full JSON object is used as the payload, key/value pairs used to construct the topic are not removed. If any topic-keys are missing, they will be omitted. For example,

• JSON: {'model':'Acurite', 'name':'5-in-1', 'temperature':32}
• Topic: home/jsonstuff/Acurite/5-in-1/value

Usage

$ json_mqtt_pub -h
usage: json_mqtt_pub [-h] [--broker BROKER] [--port PORT] [--tls]
                     [--username USERNAME] [--password PASSWORD]
                     --topic-prefix TOPIC_PREFIX [--topic-keys KEY [KEY ...]]
                     [--topic-suffix TOPIC_SUFFIX] [--retain]
                     [--status-topic STATUS_TOPIC] [--no-retain-status]
                     [--nonjson {print,error}]

Read JSON objects from stdin and publish them to MQTT.

options:
  -h, --help            show this help message and exit
  --broker BROKER       Hostname or IP address of MQTT broker (default:
                        localhost)
  --port PORT           MQTT broker port (default: 8883 for TLS, 1883
                        otherwise)
  --tls                 Use TLS to connect to broker
  --username USERNAME   MQTT broker login username
  --password PASSWORD   MQTT broker login password
  --topic-prefix TOPIC_PREFIX
                        Base topic for publishing messages
  --topic-keys KEY [KEY ...]
                        Keys whose associated values will be used to create
                        subtopics
  --topic-suffix TOPIC_SUFFIX
                        Subtopic appended to prefix and key/value subtopics
  --retain              Publish messages with retain flag set
  --status-topic STATUS_TOPIC
                        Topic to which to publish status messages
  --no-retain-status    Do not publish status messages with retain flag set
  --nonjson {print,error}
                        Action to take when non-JSON objects are received on
                        stdin. (default: print)

Arguments can be passed in a file with the '@' character.
e.g. json_mqtt_pub @path/to/args.conf

If myprog is a program that outputs JSON objects, one per line, to standard out, then

myprog | json_mqtt_publish @args.conf

will publish those JSON objects to MQTT, as defined by the arguments in args.conf.