こちらで定めた仕様を満たすクライアントです。
IOT: MQTT クライアントのサンプル
プログラム
subscribe.js
#! /usr/local/bin/node
// ---------------------------------------------------------------
// subscribe.js
//
// Oct/05/2021
//
// ---------------------------------------------------------------
'use strict'
console.error ("*** 開始 ***")
var mqtt = require('mqtt')
const client = mqtt.connect('mqtt://example.com')
const topic = 'example/test01'
var Gpio = require('onoff').Gpio
var led = new Gpio(16, 'out')
// ---------------------------------------------------------------
client.on('connect', function () {
client.subscribe(topic)
})
// ---------------------------------------------------------------
client.on('message', function (topic, message) {
const json_str = message.toString()
const dict_aa = JSON.parse (json_str)
if ('desired' in dict_aa['state'])
{
const desired = dict_aa['state']['desired']
led_proc(desired)
}
})
// ---------------------------------------------------------------
function led_proc(desired)
{
console.log(desired)
console.log(desired['led'])
const on_off = desired['led']
if (on_off == "on")
{
led.writeSync(1)
}
else if (on_off == "off")
{
led.writeSync(0)
}
report_proc(on_off)
}
// ---------------------------------------------------------------
function report_proc(on_off)
{
var dict_aa = new Object ()
dict_aa["state"] = new Object ()
dict_aa["state"]["reported"] = new Object()
dict_aa["state"]["reported"]["led"] = on_off
const json_str = JSON.stringify(dict_aa)
console.log(json_str)
console.log()
client.publish(topic, json_str)
}
// ---------------------------------------------------------------
実行スクリプト
export NODE_PATH=/usr/local/lib/node_modules
./subscribe.js
次のパージョンで確認しました。
$ node -v
v14.17.6
↧