MQTTnet/Samples/Server/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.

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 mqttFactory = new MqttFactory();

        // 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 = mqttFactory.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.
         */

        using (var mqttServer = await StartMqttServer())
        {
            // 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 mqttFactory = new MqttFactory();

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