/mqtt-demo-server

Static HTTP file server with Socket.io <-> MQTT bridge used to demonstrate how to expose MQTT to the browser

Primary LanguageJavaScriptMIT LicenseMIT

mqtt-demo-server

Static HTTP file server with Socket.io <-> MQTT bridge used to demonstrate how to expose MQTT to the browser. This demo is used in conjunction with the NodeMCU MQTT demo.

Demo Architecture

The following diagram shows the architecture for the demo. There are three (3) MQTT clients in this demo:

  1. The NodeMCU (ESP8266) board implementing the counter service
  2. The Node-Red implementation that augments a filter onto the counter service
  3. The mqtt.js client that implements the MQTT-to-socket.io bridge to expose the MQTT topics to Socket.io

Demo Architecture

Node-Red Flow for Filter

The following is the Node-Red flow that adds a filter value topic (get/ESP8266/filterValue) to the MQTT counter topic (get/ESP8266/counterValue). Also as a link.

[{"id":"80804206.7f7fc","type":"mqtt-broker","broker":"localhost","port":"1883","clientid":""},{"id":"22f2ce73.dd0d32","type":"mqtt in","name":"","topic":"get/ESP8266/counterValue","broker":"80804206.7f7fc","x":146,"y":90,"z":"1e47102.fe1b8f","wires":[["4b72bd0e.b48d44"]]},{"id":"4b72bd0e.b48d44","type":"function","name":"Filter","func":"switch (msg.topic) {\n  case \"get/ESP8266/counterValue\":\n    context.filterValue = context.filterValue || 0;\n    var filterConstant = context.filterConstant || 0.4;\n    var unfiltered = msg.payload;\n    var filtered = ((unfiltered - context.filterValue) * filterConstant) + context.filterValue;\n    context.filterValue = Math.round(filtered);\n    msg.topic = \"get/ESP8266/filterValue\";\n    msg.payload = context.filterValue;\n    return msg;\n    break;\n  case \"set/ESP8266/filterConstant\":\n    if (msg.payload >= 0.0 && msg.payload <= 1.0) {\n      context.filterConstant = msg.payload;\n      msg.topic = \"get/ESP8266/filterConstant\";\n      msg.payload = context.filterConstant;\n      msg.retain = true;\n      return msg;\n    }\n    break;\n}\n\nreturn null;","outputs":1,"x":456,"y":204,"z":"1e47102.fe1b8f","wires":[["a099df33.5f662","ec7fa690.138058"]]},{"id":"a099df33.5f662","type":"mqtt out","name":"MQTT out","topic":"","broker":"80804206.7f7fc","x":796,"y":262,"z":"1e47102.fe1b8f","wires":[]},{"id":"ec7fa690.138058","type":"debug","name":"","active":false,"console":false,"complete":false,"x":795,"y":123,"z":"1e47102.fe1b8f","wires":[]},{"id":"84c0cef8.7b3f3","type":"mqtt in","name":"","topic":"set/ESP8266/filterConstant","broker":"80804206.7f7fc","x":151,"y":248,"z":"1e47102.fe1b8f","wires":[["4b72bd0e.b48d44"]]}]