Allow access for MQTT on Ubuntu Server running on Azure

Question

I have a Ubuntu Server 14.04 running on an Azure machine. I have installed MQTT broker on this Ubuntu Server. Moreover, I have multiple ESP8266 devices that are assumed to subscribe and publish to different MQTT topics via this broker. Now my problem is that when I connect two devices to Broker, one for receiving data and other for publishing, they work fine but as I try to connect one more device to broker all devices stop working and my ESPs just display this message "trying to connect Broker" over and over again. (In endpoints of my machine I've added 1883 for HTTP, 443 for HTTPS and 22 for SSH)

My question is how I can allow multiple devices to communicate with MQTT broker running on Azure broker?

Answer 1

MQTT clients get clientID as parameter before connection to provide uniqueness. ESP8266's has unique ChipID. So use it to hit the issue. Here the example for Arduino firmware :

WiFiClient wifiClient;
PubSubClient mqttClient(wifiClient);
mqttClient.setServer(MQTT_BROKER, MQTT_BROKER_PORT);

String clientId = "IoTDevice-" + String(ESP.getChipId());
mqttClient.connect(clientId.c_str(), MQTT_USERNAME, MQTT_KEY);

Here is NodeMCU firmware example :

mqtt_cli:connect(MQTT_BROKER, MQTT_BROKER_PORT, 0, CALLBACK_FN);

mqtt_cli = mqtt.Client("IoTDevice-"..node.chipid(), 120, MQTT_USERNAME, MQTT_KEY);

Answer 2

All client devices needs to have unique client ids. The situation you have described sounds exactly like what happens if all your esp8266 devices have the same hardcoded client id