Myujth

I have a simple nodejs AWS Iot device implementation.

var awsIot = require('aws-iot-device-sdk');

const device = awsIot.device(
 keyPath: 'private.pem.key',
 certPath: 'certificate.pem.crt',
 caPath: 'CA.pem',
 clientId: 'device1',
 host: 'xxxxyyyyy1.iot.ap-southeast-1.amazonaws.com'
);

device.on('connect', () => 
 console.log('DEVICE connect!');
);
device.on('message', (topic, payload) => 
 console.log('DEVICE message!');
);
device.on('close', () => 
 console.log('DEVICE closed!');
);
device.on('error', error => 
 console.log('DEVICE error!');
 console.log(error);
);
device.on('offline', () => 
 console.log('DEVICE offline!');
);

The script runs fine if I execute a single instance of it.
Output:

dev@dev1:~/dev$ node test1.js
DEVICE connect!

However, if I run the same script on two different machines simultaneously, both devices repeatedly disconnects and reconnects.

dev@dev1:~/dev$ node test1.js
DEVICE connect!
DEVICE offline!
DEVICE closed!
DEVICE connect!
DEVICE offline!
DEVICE closed!
DEVICE connect!
DEVICE offline!
DEVICE closed!
DEVICE connect!
^C
dev@dev1:~/dev$


dev@dev2:~/dev$ node test1.js
DEVICE connect!
DEVICE offline!
DEVICE closed!
DEVICE connect!
DEVICE offline!
DEVICE closed!
DEVICE connect!
DEVICE offline!
DEVICE closed!
DEVICE connect!
^C
dev@dev2:~/dev2$

AWS Security Policy:

 "Version": "2012-10-17",
 "Statement": [
 
 "Effect": "Allow",
 "Action": "iot:*",
 "Resource": "*"
 
 ]

From AWS-IoT docs

The message broker uses the client ID to identify each client. The client ID is passed in from the client to the message broker as part of the MQTT payload. Two clients with the same client ID are not allowed to be connected concurrently to the message broker. When a client connects to the message broker using a client ID that another client is using, a CONNACK message will be sent to both clients and the currently connected client will be disconnected.

https://docs.aws.amazon.com/iot/latest/developerguide/protocols.html

Well in MQTT, the protocol AWS IoT is using, the Clientid should be unique per Device

The client identifier (ClientId) identifies each MQTT client that
connects to an MQTT broker. The broker uses the ClientID to identify
the client and the current state of the client.Therefore, this ID
should be unique per client and broker. In MQTT 3.1.1 (the current
standard), you can send an empty ClientId, if you don’t need a state
to be held by the broker. The empty ClientID results in a connection
without any state. In this case, the clean session flag must be set to
true or the broker will reject the connection.

The Client ID is also used for Client Takeover which causes your problem

Usually, a disconnected client tries to reconnect. Sometimes, the
broker still has an half-open connection for the client. In MQTT, if
the broker detects a half-open connection, it performs a ‘client
take-over’. The broker closes the previous connection to the same
client (determined by the client identifier), and establishes a new
connection with the client. This behavior ensures that the half-open
connection does not stop the disconnected client from re-establishing
a connection.

https://www.hivemq.com/blog/mqtt-essentials/