Startup.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using MqttBrokerWithDashboard.MqttBroker;
using MQTTnet.AspNetCore;
using MQTTnet.AspNetCore.Extensions;
using MudBlazor.Services;

namespace MqttBrokerWithDashboard
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddRazorPages(options => options.RootDirectory = "/Pages");
            services.AddServerSideBlazor();

            services.AddMudServices();

            services.AddSingleton<MqttBrokerService>();
            services.AddHostedMqttServerWithServices(options =>
            {
                var service = options.ServiceProvider.GetRequiredService<MqttBrokerService>();

                options.WithoutDefaultEndpoint();
                options.WithClientMessageQueueInterceptor(service);
            });
            services.AddMqttConnectionHandler();
            services.AddConnections();
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseStaticFiles();

            app.UseRouting();
            app.UseEndpoints(endpoints =>
            {
                endpoints.MapBlazorHub();
                endpoints.MapFallbackToPage("/_Host");
                endpoints.MapMqtt("/mqtt");
            });

            app.UseMqttServer(server =>
            {
                var mqttBrokerService = app.ApplicationServices.GetRequiredService<MqttBrokerService>();
                mqttBrokerService.Server = server;

                server.ClientConnectedHandler = mqttBrokerService;
                server.ClientDisconnectedHandler = mqttBrokerService;
                server.ApplicationMessageReceivedHandler = mqttBrokerService;
            });
        }
    }
}