Example code for MQTT connection

This page will help you connect to MQTT by giving examples

In PHP

<?php
declare(strict_types=1);
    echo "Hello World\n";
    require "vendor/autoload.php";

    use PhpMqtt\Client\ConnectionSettings;
    use PhpMqtt\Client\Examples\Shared\SimpleLogger;
    use PhpMqtt\Client\Exceptions\MqttClientException;
    use PhpMqtt\Client\MqttClient;
    use Psr\Log\LogLevel;

    $host = 'mqtt.grouplinknetwork.com'; #env('MQTT_HOST'),
    $port = 8883;
    $clean_session = false;

    $connectionSettings = (new ConnectionSettings)
        ->setConnectTimeout(10)
        ->setUseTls(true)
        ->setTlsSelfSignedAllowed(true)
        ->setKeepAliveInterval(60)
        ->setTlsClientCertificateFile('/home/usuario/mqttcrts/private.crt')
        ->setTlsCertificateAuthorityFile('/home/usuario/mqttcrts/grouplink-ca.crt')
        ->setTlsClientCertificateKeyFile('/home/usuario/mqttcrts/private.key');

    // echo "ConnnectionSettings:";
    // var_dump($connectionSettings);

    $mqtt = new MqttClient($host, $port, 'acquax');
    $mqtt->connect($connectionSettings, $clean_session);

    // echo "MqttClient:";
    // var_dump($mqtt);

    $mqtt->registerLoopEventHandler(function ($mqtt, float $elapsedTime) {
        if ($elapsedTime >= 590) {
            $mqtt->interrupt();
        }
    });

    $mqtt->subscribe('message/#', function ($topic, $message) {
        var_dump($topic);
        var_dump($message);
    }, 1);

    $mqtt->loop(true, false, 100);
?>

In C#

public async Task Connect_Client()
{
    try
    {
        var ca = X509Certificate.CreateFromCertFile(@"grouplink-ca.crt");
        var cert = new X509Certificate2(@"certificate-with-encrypted-key.pfx", "");

        X509Chain ch = new X509Chain();
        ch.ChainPolicy.ExtraStore.Add(ca);

        Debug.WriteLine("If");
        Debug.WriteLine(cert.Issuer);
        Debug.WriteLine(cert.IssuerName);
        Debug.WriteLine(cert.Subject);
        Debug.WriteLine(cert.SubjectName);

        var mqttFactory = new MqttFactory();

        var mqttClient = mqttFactory.CreateMqttClient();

        var mqttClientOptions = new MqttClientOptionsBuilder()
                    .WithTcpServer("mqtt.grouplinknetwork.com", 8883)
                    .WithTls(new MqttClientOptionsBuilderTlsParameters()
                    {
                        UseTls = true,
                        SslProtocol = System.Security.Authentication.SslProtocols.Tls12,
                        Certificates = new List<X509Certificate2> { cert },
                        CertificateValidationHandler = delegate { return true; }
                    })
                    .WithCleanSession()
                    .Build();

        mqttClient.ApplicationMessageReceivedAsync += e =>
        {
            Debug.WriteLine("Received application message.");
            Debug.WriteLine(e.ApplicationMessage.ConvertPayloadToString());
            return Task.CompletedTask;
        };

        var response = await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
        var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder()
            .WithTopicFilter(
                f =>
                {
                    f.WithTopic("message/gl-water-dash");
                })
            .Build();

        var res = await mqttClient.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);
        Debug.WriteLine("MQTT client subscribed to topic.");
    }
    catch (Exception ex)
    {
        Debug.WriteLine("Exception");
        Debug.WriteLine(ex.Message);
    }

    finally
    {
        Debug.WriteLine("Finally");
    }
}

In JS

const mqtt = require("mqtt");
const fs = require("fs");

const caFile = fs.readFileSync("grouplink-ca.crt");
const certFile = fs.readFileSync("private.crt");
const keyFile = fs.readFileSync("private.key");

const options = {
  protocol: "mqtts",
  host: "mqtt.grouplinknetwork.com",
  port: 8883,
  ca: [caFile],
  cert: certFile,
  key: keyFile,
  rejectUnauthorized: true,
  clean: false, // default is true = remove messages when disconnected
  clientId: 'yourOrgName', // update here, set with your org name
};

const client = mqtt.connect(options);
const topic = "message/your-org-name"; // update here
console.log("connecting...");

client.on("connect", function () {
  console.log("connected");
  client.subscribe(topic, {
    qos: 1, // at least once delivery
  },function (err) {
    if (!err) {
      console.log("subscribed to " + topic);
    }
  });
});

client.on("disconnect", function () {
  console.log("disconnected!");
});

client.on("offline", function () {
  // in small disconnections, there is a chance that mqtt will
  // reconnect and consume again, so it's just a log
  console.log("offline!");
});

client.on("error", function (e) {
  console.log("error: " + JSON.stringify(e));
  // flush to the database, mark error status, it reached here,
  // the lib will stop trying to reconnect
  process.exit(1);
});

client.on("message", function (topic, message) {
  // send it to your persistence queue/layer
  console.log(message.toString());
});