This is an MQTT client example project that showcases how you can use HiveMQ Cloud with the Dart Client. The example project covers the basic MQTT functionality: Connecting MQTT clients to your HiveMQ Cloud cluster, subscribing to topics and publishing data (sending and receiving messages using the MQTT protocol).
The Dart client used here supports MQTT v3.1 and v3.1.1. You can find documentation for this client library here: https://www.hivemq.com/blog/mqtt-client-library-mqtt-dart/.
This example repository is easily and clearly structured, so you can start quickly:
This readme file is your starting point. Here we will describe what you have to do step-by-step to get started with this example.
main.dart in the bin directory is a simple implementation that demonstrates the core functionality of an MQTT Client.
Follow the instructions in the following paragraphs to get started yourself.
HiveMQ is the industry leader for enterprise-ready, beautifully scalable, large-scale IoT deployments with MQTT. We help companies connect things to the Internet. Our MQTT-based messaging platform ensures fast, reliable, and secure movement of data to and from connected IoT devices for companies around the world. HiveMQ Cloud is our fully-managed, cloud-native IoT messaging platform that makes trustworthy and scalable IoT device connectivity simple. You can learn more about HiveMQ Cloud on our website, documentation and our blog posts.
By signing up for HiveMQ Cloud you will automatically get access to a HiveMQ Cloud Basic cluster. HiveMQ Cloud Basic is our smallest package that allows you to connect up to 100 MQTT clients for free and test the full MQTT functionality.
The HiveMQ Cloud Quick Start Guide gives you step-by-step instructions on how to set up your HiveMQ Cloud account, create clusters, and connect MQTT clients.
After signing up, you have a running HiveMQ Cloud cluster, that you can use in this example. Now clone this repository into your local IDE.
For using the code examples, you need to install the necessary client library.
The correct dependencies are listed in the pubspec.yaml.
Execute this command in the terminal of your IDE to get the right dependencies.
dart pub getTo define the HiveMQ Cloud cluster which should be targeted, you need to fill the placeholders in the code with your host name, username and password.
The host name can be found in the Details section of the Overview tab of your cluster.
After the cluster is created, add a set of credentials that you can use in this example or future implementations.
Use any secure username and password you desire.
The username and password are the values used as Client Credentials that you just created.
This example project covers the core functionality of an MQTT client interacting with HiveMQ Cloud.
To securely connect the MQTT client with HiveMQ Cloud you need to enable TLS.
Use your username and password, to authenticate your MQTT client at HiveMQ Cloud.
To connect the client, use the port 8883 that is standard for secure MQTT communication.
'<your_name>' is the name you give your client, you can choose any name for this.
await client.connect('<your_username>', '<your_password>');client = MqttServerClient.withPort('<your_host>', '<your_name>', <your_port>);The code located inside main.dart connects to the configured HiveMQ Cloud Broker in a simple way.
This is a ready-set example that can simply be run after inputting your credentials.
Navigate to the bin directory and run main.dart in your terminal.
cd bin
dart main.dartThe different processes are all defined in their respective functions.
These get all called in the prepareMqttClient() function at the start, which in turn gets called by the main function with newclient.prepareMqttClient().
After connecting the client, the code first subscribes to the topic filter "Dart/Mqtt_client/testtopic".
That means the MQTT client receives all messages that are published to this topic filter.
void _subscribeToTopic(String topicName) {
print('Subscribing to the $topicName topic');
client.subscribe(topicName, MqttQos.atMostOnce);
// print the message when it is received
client.updates.listen((List<MqttReceivedMessage<MqttMessage>> c) {
final MqttPublishMessage recMess = c[0].payload;
var message = MqttPublishPayload.bytesToStringAsString(recMess.payload.message);
print('YOU GOT A NEW MESSAGE:');
print(message);
});
}The _onSubscribed callback acts as a reassurance that the subscription worked.
Then the code publishes a message to the same topic with _publishMessage.
The message gets printed to the terminal by the _subscribeToTopic method, that listens for incoming messages.
void _publishMessage(String message) {
final MqttClientPayloadBuilder builder = MqttClientPayloadBuilder();
builder.addString(message);
print('Publishing message "$message" to topic ${'Dart/Mqtt_client/testtopic'}');
client.publishMessage('Dart/Mqtt_client/testtopic', MqttQos.exactlyOnce, builder.payload);
}If you want to learn more about MQTT, visit the MQTT Essentials guide, that explains the core of MQTT concepts, its features and other essential information. Learn about Dart, a client-optimized programming language for fast apps on any platform, on their website. Also have a look at the client library.
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