> For the complete documentation index, see [llms.txt](https://rhiot.gitbook.io/rhiotdocumentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://rhiot.gitbook.io/rhiotdocumentation/index-5/mqtt_cloudlet_quickstart.md).

# MQTT Cloudlet quickstart

The MQTT cloudlet quickstart can be used as a base for the fat-jar MQTT microservices.

## Creating and running the MQTT cloudlet project

In order to create the MQTT cloudlet project execute the following commands:

```
git clone git@github.com:rhiot/quickstarts.git
cp -r quickstarts/cloudlets/mqtt mqtt
cd mqtt
mvn install
```

To start the MQTT cloudlet execute the following command:

```
java -jar target/rhiot-cloudlets-mqtt-1.0.0-SNAPSHOT.jar
```

You can also build and run it as a Docker image (we love Docker and recommend this approach):

```
TARGET_IMAGE=yourUsername/rhiot-cloudlets-mqtt
mvn install docker:build docker:push -Ddocker.image.target=${TARGET_IMAGE}
docker run -it ${TARGET_IMAGE}
```

## MQTT broker

By default MQTT cloudlet quickstart starts embedded [ActiveMQ](http://activemq.apache.org) MQTT broker (on 1883 port). If you would like to connect your cloudlet application to the external ActiveMQ broker (instead of starting the embedded one), run the cloudlet with the `BROKER_URL` environment variable or system property, for example:

```
java -DBROKER_URL=tcp://amqbroker.example.com:61616 -jar target/rhiot-cloudlets-mqtt-1.0.0-SNAPSHOT.jar
```

...or...

```
docker run -e BROKER_URL=tcp://amqbroker.example.com:61616 -it yourUsername/rhiot-cloudlets-mqtt
```

## Sample chat application

The MQTT cloudlet quickstart is in fact a simple chat application. Clients can send the messages to the chat channel by subscribing to the broker and sending the messages to the `chat` MQTT topic. To send some messages to the chat you can use the standalone [MQTT.js](https://www.npmjs.com/package/mqtt) client:

```
mqtt pub -t 'chat' -h 'localhost' -m 'Hello, this is the IoT device!'
mqtt pub -t 'chat' -h 'localhost' -m 'I just wanted to say hello!'
mqtt pub -t 'chat' -h 'localhost' -m 'Hello, IoT device. Nice to meet you!'
```

The clients can subscribe to the chat updates by listening on the `chat-updates` MQTT topic - whenever the new message has been sent to the chat, the clients registered to the `chat-updates` will receive the updated chat history.

The quickstart also exposed the simple REST API that can be used to read the chat history using the HTTP `GET` request:

```
$ curl http://localhost:8181/chat
Hello, this is the IoT device!
I just wanted to say hello!
Hello, IoT device. Nice to meet you!
```

## Architectural overview

When MQTT cloudlet is started with the embedded ActiveMQ broker, the architecture of the example is the following:

![](https://github.com/rhiot/rhiotdocumentation/tree/8c31a9d7d4bee1680d83639cefa800bec2a1f8df/quickstarts/images/quickstarts_cloudlet_mqtt_embedded.png)

When you connect to the external ActiveMQ broker (using `BROKER_URL` option), the architecture of the example becomes more like the following diagram:

![](https://github.com/rhiot/rhiotdocumentation/tree/8c31a9d7d4bee1680d83639cefa800bec2a1f8df/quickstarts/images/quickstarts_cloudlet_mqtt_external.png)


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