ReactNative MQTT Listener - node.js

Question

I have the following code excerpt:
client.on ('message', function (msg) {
// ....
});
Can someone tell me how I get the value of msg from this function and can access it from outside.
I tried but it doesn't work:
this.setState ({msg: msg})

Answer 1

You can make an MQTT manager and use it.
Example
module.exports = { // cached singleton instance
QOS: 1, // Only 0 and 1 supported by Rabbit
props: null,
create(userID, connectionProps = {}) {
if (userID && connectionProps) {
// http://www.hivemq.com/demos/websocket-client/
this.onConnectionOpened = this.onConnectionOpened.bind(this);
this.onConnectionClosed = this.onConnectionClosed.bind(this);
this.onError = this.onError.bind(this);
this.onMessageArrived = this.onMessageArrived.bind(this);
this.disconnect = this.disconnect.bind(this);
const deviceId = this.randIdCreator()
.replace(/[^a-zA-Z0-9]+/g, '');
this.conProps = _.extend({
clientId: `realtime.${userID}.${deviceId}`,
channelToUse: `mqtt-subscription-realtime.${userID}`,
auth: false,
clean: true, // clean session YES deletes the queue when all clients disconnect
}, connectionProps);
/* create mqtt client */
MQTT.createClient(this.conProps)
.then((client) => {
this.client = client;
client.on('closed', this.onConnectionClosed);
client.on('error', this.onError);
client.on('message', this.onMessageArrived);
client.on('connect', this.onConnectionOpened);
client.connect();
}).catch((err) => {
console.error(`MQTT.createtClient error: ${err}`);
});
}
},
...
onMessageArrived(message) {
if (message) {
console.log(`MQTT New message: ${JSON.stringify(message)}`)
}
}
...
Usage
import MqttNotificationsManager from './realtimeManager';
// init realtime
MqttNotificationsManager.create(
'bob',
{
uri: 'mqtt://test.mosquitto.org:1883',
},
);