MQTTnet/Samples/Client/Client_Subscribe_Samples.cs

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

// ReSharper disable UnusedType.Global
// ReSharper disable UnusedMember.Global
// ReSharper disable InconsistentNaming

using MQTTnet.Client;
using MQTTnet.Samples.Shared;

namespace MQTTnet.Samples.Client;

public static class Client_Subscribe_Samples
{
    public static async Task Handle_Received_Application_Message()
    {
        /*
         * This sample subscribes to a topic and processes the received message.
         */

        var mqttFactory = new MqttFactory();

        using (var mqttClient = mqttFactory.CreateMqttClient())
        {
            var mqttClientOptions = new MqttClientOptionsBuilder()
                .WithTcpServer("broker.hivemq.com")
                .Build();

            // Setup message handling before connecting so that queued messages
            // are also handled properly. When there is no event handler attached all
            // received messages get lost.
            mqttClient.ApplicationMessageReceivedAsync += e =>
            {
                Console.WriteLine("Received application message.");
                e.DumpToConsole();

                return Task.CompletedTask;
            };

            await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);

            var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder()
                .WithTopicFilter(f => { f.WithTopic("mqttnet/samples/topic/2"); })
                .Build();

            await mqttClient.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);

            Console.WriteLine("MQTT client subscribed to topic.");

            Console.WriteLine("Press enter to exit.");
            Console.ReadLine();
        }
    }

    public static async Task Subscribe_Topic()
    {
        /*
         * This sample subscribes to a topic.
         */

        var mqttFactory = new MqttFactory();

        using (var mqttClient = mqttFactory.CreateMqttClient())
        {
            var mqttClientOptions = new MqttClientOptionsBuilder()
                .WithTcpServer("broker.hivemq.com")
                .Build();

            await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);

            var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder()
                .WithTopicFilter(f => { f.WithTopic("mqttnet/samples/topic/1"); })
                .Build();

            var response = await mqttClient.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);

            Console.WriteLine("MQTT client subscribed to topic.");

            // The response contains additional data sent by the server after subscribing.
            response.DumpToConsole();
        }
    }
}