SOMS/test/MqttConsoleAppClient/MqttClient.cs

using System.Security.Authentication;
using MqttConsoleAppClient;
using MQTTnet;
using MQTTnet.Client;
using MQTTnet.Formatter;
namespace MQTTnet.Samples.Client;

public static class Client_Connection_Samples
{
    public static async Task Connect_Client()
    {
        /*
         * This sample creates a simple MQTT client and connects to a public broker.
         *
         * Always dispose the client when it is no longer used.
         * The default version of MQTT is 3.1.1.
         */

        var mqttFactory = new MqttFactory();

        using (var mqttClient = mqttFactory.CreateMqttClient())
        {
            // Use builder classes where possible in this project.
            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("127.0.0.1").Build();

            // This will throw an exception if the server is not available.
            // The result from this message returns additional data which was sent 
            // from the server. Please refer to the MQTT protocol specification for details.
            var response = await mqttClient.ConnectAsync(mqttClientOptions);
            mqttClient.PublishAsync(new MqttApplicationMessage() { });
            mqttClient.ApplicationMessageReceivedAsync += MqttClient_ApplicationMessageReceivedAsync;
            Console.WriteLine("The MQTT client is connected.");
            response.DumpToConsole();
            Console.ReadLine();
            // Send a clean disconnect to the server by calling _DisconnectAsync_. Without this the TCP connection
            // gets dropped and the server will handle this as a non clean disconnect (see MQTT spec for details).
            //var mqttClientDisconnectOptions = mqttFactory.CreateClientDisconnectOptionsBuilder().Build();

            //await mqttClient.DisconnectAsync(mqttClientDisconnectOptions, CancellationToken.None);
        }
    }

    private static Task MqttClient_ApplicationMessageReceivedAsync(MqttApplicationMessageReceivedEventArgs arg)
    {
        throw new NotImplementedException();
    }

    public static async Task Connect_Client_Timeout()
    {
        /*
         * This sample creates a simple MQTT client and connects to an invalid broker using a timeout.
         * 
         * This is a modified version of the sample _Connect_Client_! See other sample for more details.
         */

        var mqttFactory = new MqttFactory();

        using (var mqttClient = mqttFactory.CreateMqttClient())
        {
            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("127.0.0.1").Build();

            try
            {
                using (var timeoutToken = new CancellationTokenSource(TimeSpan.FromHours(1)))
                {
                    await mqttClient.ConnectAsync(mqttClientOptions, timeoutToken.Token);
                }
            }
            catch (OperationCanceledException)
            {
                Console.WriteLine("Timeout while connecting.");
            }
        }
    }

    public static async Task Connect_Client_Using_MQTTv5()
    {
        /*
         * This sample creates a simple MQTT client and connects to a public broker using MQTTv5.
         * 
         * This is a modified version of the sample _Connect_Client_! See other sample for more details.
         */

        var mqttFactory = new MqttFactory();

        using (var mqttClient = mqttFactory.CreateMqttClient())
        {
            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").WithProtocolVersion(MqttProtocolVersion.V500).Build();

            // In MQTTv5 the response contains much more information.
            var response = await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);

            Console.WriteLine("The MQTT client is connected.");

            response.DumpToConsole();
        }
    }

    public static async Task Connect_Client_Using_TLS_1_2()
    {
        /*
         * This sample creates a simple MQTT client and connects to a public broker using TLS 1.2 encryption.
         * 
         * This is a modified version of the sample _Connect_Client_! See other sample for more details.
         */

        var mqttFactory = new MqttFactory();

        using (var mqttClient = mqttFactory.CreateMqttClient())
        {
            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("mqtt.fluux.io")
                .WithTls(
                    o =>
                    {
                        // The used public broker sometimes has invalid certificates. This sample accepts all
                        // certificates. This should not be used in live environments.
                        o.CertificateValidationHandler = _ => true;

                        // The default value is determined by the OS. Set manually to force version.
                        o.SslProtocol = SslProtocols.Tls12;
                    })
                .Build();

            using (var timeout = new CancellationTokenSource(5000))
            {
                await mqttClient.ConnectAsync(mqttClientOptions, timeout.Token);

                Console.WriteLine("The MQTT client is connected.");
            }
        }
    }

    public static async Task Connect_Client_Using_WebSockets()
    {
        /*
         * This sample creates a simple MQTT client and connects to a public broker using a WebSocket connection.
         * 
         * This is a modified version of the sample _Connect_Client_! See other sample for more details.
         */

        var mqttFactory = new MqttFactory();

        using (var mqttClient = mqttFactory.CreateMqttClient())
        {
            var mqttClientOptions = new MqttClientOptionsBuilder().WithWebSocketServer("broker.hivemq.com:8000/mqtt").Build();

            var response = await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);

            Console.WriteLine("The MQTT client is connected.");

            response.DumpToConsole();
        }
    }

    public static async Task Connect_Client_With_TLS_Encryption()
    {
        /*
         * This sample creates a simple MQTT client and connects to a public broker with enabled TLS encryption.
         * 
         * This is a modified version of the sample _Connect_Client_! See other sample for more details.
         */

        var mqttFactory = new MqttFactory();

        using (var mqttClient = mqttFactory.CreateMqttClient())
        {
            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("test.mosquitto.org", 8883)
                .WithTls(
                    o =>
                    {
                        // The used public broker sometimes has invalid certificates. This sample accepts all
                        // certificates. This should not be used in live environments.
                        o.CertificateValidationHandler = _ => true;
                    })
                .Build();

            // In MQTTv5 the response contains much more information.
            using (var timeout = new CancellationTokenSource(5000))
            {
                var response = await mqttClient.ConnectAsync(mqttClientOptions, timeout.Token);

                Console.WriteLine("The MQTT client is connected.");

                response.DumpToConsole();
            }
        }
    }

    public static async Task Inspect_Certificate_Validation_Errors()
    {
        /*
         * This sample prints the certificate information while connection. This data can be used to decide whether a connection is secure or not
         * including the reason for that status.
         */

        var mqttFactory = new MqttFactory();

        using (var mqttClient = mqttFactory.CreateMqttClient())
        {
            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("mqtt.fluux.io", 8883)
                .WithTls(
                    o =>
                    {
                        o.CertificateValidationHandler = eventArgs =>
                        {
                            eventArgs.Certificate.Subject.DumpToConsole();
                            eventArgs.Certificate.GetExpirationDateString().DumpToConsole();
                            eventArgs.Chain.ChainPolicy.RevocationMode.DumpToConsole();
                            eventArgs.Chain.ChainStatus.DumpToConsole();
                            eventArgs.SslPolicyErrors.DumpToConsole();
                            return true;
                        };
                    })
                .Build();

            // In MQTTv5 the response contains much more information.
            using (var timeout = new CancellationTokenSource(5000))
            {
                await mqttClient.ConnectAsync(mqttClientOptions, timeout.Token);
            }
        }
    }

    public static async Task Ping_Server()
    {
        /*
         * This sample sends a PINGREQ packet to the server and waits for a reply.
         *
         * This is only supported in METTv5.0.0+.
         */

        var mqttFactory = new MqttFactory();

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

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

            // This will throw an exception if the server does not reply.
            await mqttClient.PingAsync(CancellationToken.None);

            Console.WriteLine("The MQTT server replied to the ping request.");
        }
    }

    public static async Task Reconnect_Using_Event()
    {
        /*
         * This sample shows how to reconnect when the connection was dropped.
         * This approach uses one of the events from the client.
         * This approach has a risk of dead locks! Consider using the timer approach (see sample).
         */

        var mqttFactory = new MqttFactory();

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

            mqttClient.DisconnectedAsync += async e =>
            {
                if (e.ClientWasConnected)
                {
                    // Use the current options as the new options.
                    await mqttClient.ConnectAsync(mqttClient.Options);
                }
            };

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

    public static void Reconnect_Using_Timer()
    {
        /*
         * This sample shows how to reconnect when the connection was dropped.
         * This approach uses a custom Task/Thread which will monitor the connection status.
         * This is the recommended way but requires more custom code!
         */

        var mqttFactory = new MqttFactory();

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

            _ = Task.Run(
                async () =>
                {
                    // User proper cancellation and no while(true).
                    while (true)
                    {
                        try
                        {
                            // This code will also do the very first connect! So no call to _ConnectAsync_ is required
                            // in the first place.
                            if (!mqttClient.IsConnected)
                            {
                                await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);

                                // Subscribe to topics when session is clean etc.

                                Console.WriteLine("The MQTT client is connected.");
                            }
                        }
                        catch
                        {
                            // Handle the exception properly (logging etc.).
                        }
                        finally
                        {
                            // Check the connection state every 5 seconds and perform a reconnect if required.
                            await Task.Delay(TimeSpan.FromSeconds(5));
                        }
                    }
                });
        }
    }
}