Server_Simple_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.Diagnostics.Logger;
using MQTTnet.Protocol;
using MQTTnet.Server;

namespace MQTTnet.Samples.Server;

public static class Server_Simple_Samples
{
    public static async Task Force_Disconnecting_Client()
    {
        /*
         * This sample will disconnect a client.
         *
         * See _Run_Minimal_Server_ for more information.
         */

        using (var mqttServer = await StartMqttServer())
        {
            // Let the client connect.
            await Task.Delay(TimeSpan.FromSeconds(5));

            // Now disconnect the client (if connected).
            var affectedClient = (await mqttServer.GetClientsAsync()).FirstOrDefault(c => c.Id == "MyClient");
            if (affectedClient != null)
            {
                await affectedClient.DisconnectAsync();
            }
        }
    }

    public static async Task Publish_Message_From_Broker()
    {
        /*
         * This sample will publish a message directly at the broker.
         *
         * See _Run_Minimal_Server_ for more information.
         */

        using (var mqttServer = await StartMqttServer())
        {
            // Create a new message using the builder as usual.
            var message = new MqttApplicationMessageBuilder().WithTopic("HelloWorld").WithPayload("Test").Build();

            // Now inject the new message at the broker.
            await mqttServer.InjectApplicationMessage(
                new InjectedMqttApplicationMessage(message)
                {
                    SenderClientId = "SenderClientId"
                });
        }
    }

    public static async Task Run_Minimal_Server()
    {
        /*
         * This sample starts a simple MQTT server which will accept any TCP connection.
         */

        var mqttServerFactory = new MqttServerFactory();

        // The port for the default endpoint is 1883.
        // The default endpoint is NOT encrypted!
        // Use the builder classes where possible.
        var mqttServerOptions = new MqttServerOptionsBuilder().WithDefaultEndpoint().Build();

        // The port can be changed using the following API (not used in this example).
        // new MqttServerOptionsBuilder()
        //     .WithDefaultEndpoint()
        //     .WithDefaultEndpointPort(1234)
        //     .Build();

        using (var mqttServer = mqttServerFactory.CreateMqttServer(mqttServerOptions))
        {
            await mqttServer.StartAsync();

            Console.WriteLine("Press Enter to exit.");
            Console.ReadLine();

            // Stop and dispose the MQTT server if it is no longer needed!
            await mqttServer.StopAsync();
        }
    }

    public static async Task Run_Server_With_Logging()
    {
        /*
         * This sample starts a simple MQTT server and prints the logs to the output.
         *
         * IMPORTANT! Do not enable logging in live environment. It will decrease performance.
         *
         * See sample "Run_Minimal_Server" for more details.
         */

        var mqttServerFactory = new MqttServerFactory(new ConsoleLogger());

        var mqttServerOptions = new MqttServerOptionsBuilder().WithDefaultEndpoint().Build();

        using (var mqttServer = mqttServerFactory.CreateMqttServer(mqttServerOptions))
        {
            await mqttServer.StartAsync();

            Console.WriteLine("Press Enter to exit.");
            Console.ReadLine();

            // Stop and dispose the MQTT server if it is no longer needed!
            await mqttServer.StopAsync();
        }
    }

    public static async Task Validating_Connections()
    {
        /*
         * This sample starts a simple MQTT server which will check for valid credentials and client ID.
         *
         * See _Run_Minimal_Server_ for more information.
         */

        var mqttServerFactory = new MqttServerFactory();

        var mqttServerOptions = new MqttServerOptionsBuilder().WithDefaultEndpoint().Build();

        using (var mqttServer = mqttServerFactory.CreateMqttServer(mqttServerOptions))
        {
            // Setup connection validation before starting the server so that there is
            // no change to connect without valid credentials.
            mqttServer.ValidatingConnectionAsync += e =>
            {
                if (e.ClientId != "ValidClientId")
                {
                    e.ReasonCode = MqttConnectReasonCode.ClientIdentifierNotValid;
                }

                if (e.UserName != "ValidUser")
                {
                    e.ReasonCode = MqttConnectReasonCode.BadUserNameOrPassword;
                }

                if (e.Password != "SecretPassword")
                {
                    e.ReasonCode = MqttConnectReasonCode.BadUserNameOrPassword;
                }

                return Task.CompletedTask;
            };

            await mqttServer.StartAsync();

            Console.WriteLine("Press Enter to exit.");
            Console.ReadLine();

            await mqttServer.StopAsync();
        }
    }

    static async Task<MqttServer> StartMqttServer()
    {
        var mqttServerFactory = new MqttServerFactory();

        // Due to security reasons the "default" endpoint (which is unencrypted) is not enabled by default!
        var mqttServerOptions = mqttServerFactory.CreateServerOptionsBuilder().WithDefaultEndpoint().Build();
        var server = mqttServerFactory.CreateMqttServer(mqttServerOptions);
        await server.StartAsync();
        return server;
    }

    class ConsoleLogger : IMqttNetLogger
    {
        readonly object _consoleSyncRoot = new();

        public bool IsEnabled => true;

        public void Publish(MqttNetLogLevel logLevel, string source, string message, object[]? parameters, Exception? exception)
        {
            var foregroundColor = ConsoleColor.White;
            switch (logLevel)
            {
                case MqttNetLogLevel.Verbose:
                    foregroundColor = ConsoleColor.White;
                    break;

                case MqttNetLogLevel.Info:
                    foregroundColor = ConsoleColor.Green;
                    break;

                case MqttNetLogLevel.Warning:
                    foregroundColor = ConsoleColor.DarkYellow;
                    break;

                case MqttNetLogLevel.Error:
                    foregroundColor = ConsoleColor.Red;
                    break;
            }

            if (parameters?.Length > 0)
            {
                message = string.Format(message, parameters);
            }

            lock (_consoleSyncRoot)
            {
                Console.ForegroundColor = foregroundColor;
                Console.WriteLine(message);

                if (exception != null)
                {
                    Console.WriteLine(exception);
                }
            }
        }
    }
}