MQTT.js: パブリック MQTT ブローカーの使い方

Publish

pub01.js

const mqtt = require("mqtt")
// const host = "test.mosquitto.org"
const host = "broker.emqx.io"
const client = mqtt.connect("mqtt://" + host)

const topic_target = "test_topic/aaa"
client.on("connect", () => {
  client.subscribe(topic_target, (err) => {
    if (!err) {
      client.publish(topic_target, "Hello mqtt Feb/09/2025 PM 18:12")
  client.end()
    }
  })
})

実行コマンド

go_pub01.sh

export NODE_PATH=/usr/local/lib/node_modules
node pub01.js

Subscribe

sub01.js

const mqtt = require("mqtt")
// const host = "test.mosquitto.org"
const host = "broker.emqx.io"
const client = mqtt.connect("mqtt://" + host)

const topic_target = "test_topic/aaa"
client.on("connect", () => {
  client.subscribe(topic_target, (err) => {
    if (!err) {
	console.log("*** subscribed *** " + topic_target)
    }
  })
})

client.on("message", (topic, message) => {
  // message is Buffer
  console.log(topic.toString())
  console.log(message.toString())
//  client.end()
})

実行コマンド

go_sub01.sh

export NODE_PATH=/usr/local/lib/node_modules
node sub01.js

実行結果

$ ./go_sub01.sh 
*** subscribed *** test_topic/aaa
test_topic/aaa
Hello mqtt Feb/09/2025 PM 18:12