MQTT Topic Filter

A subflow to compliment MQTT style topics (for use with or without MQTT)

About

This subflow node permits you to use MQTT style filtering.

e.g...

  • home/+/temperature
    • will match home/bedroom/temperature
    • will match home/livingroom/temperature
    • will not match home/room/1/temperature
    • will not match room/1/temperature
  • home/#
    • will match home/location
    • will match home/livingroom/temperature
    • will match home/livingroom/humidity
    • will not match room/1/temperature

Using subflow

Import the attached flow then locate it in the pallete & drag onto the editor

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Demo

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[{"id":"mqtt-topic-filter","type":"subflow","name":"topic filter","info":"## MQTT Topic filter\n\n### Description\nFilters messages based on the value of `msg.topic` using standard MQTT topic filter notation.\n* `#` match all\n* `+` match one level\n\n### example filters\n* `home/+/temperature` \n  * will match `home/bedroom/temperature`\n  * will match `home/livingroom/temperature`\n  * will not match `home/room/1/temperature`\n  * will not match `room/1/temperature`\n* `home/#` \n  * will match `home/location`\n  * will match `home/livingroom/temperature`\n  * will match `home/livingroom/humidity`\n  * will not match `room/1/temperature`\n\n\n### Outputs\n\n#### Output 1 - match\nMessages with a topic that matches the `topic filter` will be sent out this output.\n\n#### Output 2 - no match\nMessages with a topic that does not match the `topic filter` will be sent out this output to permit next level filtering\n","category":"function","in":[{"x":68,"y":80,"wires":[{"id":"c7fc11c3.07902"}]}],"out":[{"x":340,"y":48,"wires":[{"id":"c7fc11c3.07902","port":0}]},{"x":340,"y":96,"wires":[{"id":"c7fc11c3.07902","port":1}]}],"env":[{"name":"filter","type":"str","value":"","ui":{"label":{"en-US":"Topic filter"},"type":"input","opts":{"types":["str"]}}},{"name":"status","type":"bool","value":"true","ui":{"label":{"en-US":"Show topic"},"type":"input","opts":{"types":["bool"]}}}],"meta":{"type":"mqtt-topic-filter","version":"1.0.0","author":"steve-mcl","desc":"A node to filter MQTT topics","keywords":"mqtt","license":"MIT"},"color":"#D8BFD8","outputLabels":["Match","No Match"],"icon":"font-awesome/fa-filter","status":{"x":548,"y":160,"wires":[{"id":"519579c5.dfaec8","port":0},{"id":"4ce4687e.e359a8","port":0}]}},{"id":"c7fc11c3.07902","type":"function","z":"mqtt-topic-filter","name":"filter","func":"var a = msg.topic;\nvar b = env.get(\"filter\") || '#';\n\nif(a===b) { return [msg, null]; }\nif(b==='#') { \n    if(a) return [msg, null]; //if topic is something, OK\n    return [null, msg];//otherwise, fail!\n}\nvar nameSegments = a.split('/');\nvar filterSegments = b.split('/');\nfor (var i = 0; i < filterSegments.length; i++) {\n    var topicSegment = nameSegments[i];\n    var patternSegment = filterSegments[i];\n    var match = false;\n    if(topicSegment === patternSegment) { match = true; }\n    if(patternSegment === '+') { match = true; }\n    if(patternSegment === '#') {  return [msg, null]; }\n    if(match === false) { return [null, msg]; }\n}\nif(nameSegments.length !== filterSegments.length) { return [null, msg]; }\n\nreturn [msg, null];\n","outputs":2,"noerr":0,"initialize":"","finalize":"","x":192,"y":80,"wires":[[],[]]},{"id":"c52c30b1.8341","type":"inject","z":"mqtt-topic-filter","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":true,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":148,"y":160,"wires":[["45ee843e.ec4bbc"]]},{"id":"519579c5.dfaec8","type":"function","z":"mqtt-topic-filter","name":"","func":"var b = env.get(\"filter\") || '#';\nnode.status({text:b})\nmsg.payload = b;\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","x":428,"y":144,"wires":[[]]},{"id":"45ee843e.ec4bbc","type":"switch","z":"mqtt-topic-filter","name":"","property":"status","propertyType":"env","rules":[{"t":"true"},{"t":"else"}],"checkall":"true","repair":false,"outputs":2,"x":290,"y":160,"wires":[["519579c5.dfaec8"],["4ce4687e.e359a8"]]},{"id":"4ce4687e.e359a8","type":"function","z":"mqtt-topic-filter","name":"","func":"node.status({})\ndelete msg.payload;\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","x":428,"y":192,"wires":[[]]}]

Flow Info

Created 3 years, 3 months ago
Rating: 5 1

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Node Types

Core
  • function (x3)
  • inject (x1)
  • switch (x1)
Other
  • subflow (x1)

Tags

  • mqtt
  • topic
  • filter
Copy this flow JSON to your clipboard and then import into Node-RED using the Import From > Clipboard (Ctrl-I) menu option