MQTTnet/Samples/Client/Client_Connection_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 System.Security.Authentication;
using System.Security.Cryptography.X509Certificates;
using MQTTnet.Client;
using MQTTnet.Extensions.WebSocket4Net;
using MQTTnet.Formatter;
using MQTTnet.Samples.Helpers;

namespace MQTTnet.Samples.Client;

public static class Client_Connection_Samples
{
    public static async Task Clean_Disconnect()
    {
        /*
         * This sample disconnects in a clean way. This will send a MQTT DISCONNECT packet
         * to the server and close the connection afterwards.
         *
         * See sample _Connect_Client_ for more details.
         */

        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 send the DISCONNECT packet. Calling _Dispose_ without DisconnectAsync the 
            // connection is closed in a "not clean" way. See MQTT specification for more details.
            await mqttClient.DisconnectAsync(new MqttClientDisconnectOptionsBuilder().WithReason(MqttClientDisconnectOptionsReason.NormalDisconnection).Build());
        }
    }

    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("broker.hivemq.com").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, CancellationToken.None);

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

            response.DumpToConsole();

            // 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);
        }
    }

    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.FromSeconds(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")
                .WithTlsOptions(
                    o =>
                    {
                        // The used public broker sometimes has invalid certificates. This sample accepts all
                        // certificates. This should not be used in live environments.
                        o.WithCertificateValidationHandler(_ => true);

                        // The default value is determined by the OS. Set manually to force version.
                        o.WithSslProtocols(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_WebSocket4Net()
    {
        /*
         * This sample creates a simple MQTT client and connects to a public broker using a WebSocket connection.
         * Instead of the .NET implementation of WebSockets the implementation from WebSocket4Net is used. It provides more
         * encryption algorithms and supports more platforms.
         * 
         * This is a modified version of the sample _Connect_Client_! See other sample for more details.
         */

        var mqttFactory = new MqttFactory().UseWebSocket4Net();

        using (var mqttClient = mqttFactory.CreateMqttClient())
        {
            var mqttClientOptions = new MqttClientOptionsBuilder().WithWebSocketServer(o => o.WithUri("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_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(o => o.WithUri("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)
                .WithTlsOptions(
                    o => o.WithCertificateValidationHandler(
                        // The used public broker sometimes has invalid certificates. This sample accepts all
                        // certificates. This should not be used in live environments.
                        _ => 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 Connect_With_Amazon_AWS()
    {
        /*
         * This sample creates a simple MQTT client and connects to an Amazon Web Services broker.
         *
         * The broker requires special settings which are set here.
         */

        var mqttFactory = new MqttFactory();

        using (var mqttClient = mqttFactory.CreateMqttClient())
        {
            var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("amazon.web.services.broker")
                // Disabling packet fragmentation is very important!  
                .WithoutPacketFragmentation()
                .Build();

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

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

            await mqttClient.DisconnectAsync();
        }
    }

    public static async Task Disconnect_Clean()
    {
        /*
         * This sample disconnects from the server with sending a DISCONNECT packet.
         * This way of disconnecting is treated as a clean disconnect which will not
         * trigger sending the last will etc.
         */

        var mqttFactory = new MqttFactory();

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

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

            // Calling _DisconnectAsync_ will send a DISCONNECT packet before closing the connection.
            // Using a reason code requires MQTT version 5.0.0!
            await mqttClient.DisconnectAsync(MqttClientDisconnectOptionsReason.ImplementationSpecificError);
        }
    }

    public static async Task Disconnect_Non_Clean()
    {
        /*
         * This sample disconnects from the server without sending a DISCONNECT packet.
         * This way of disconnecting is treated as a non clean disconnect which will
         * trigger sending the last will etc.
         */

        var mqttFactory = new MqttFactory();

        var mqttClient = mqttFactory.CreateMqttClient();

        var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("broker.hivemq.com").Build();

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

        // Calling _Dispose_ or use of a _using_ statement will close the transport connection
        // without sending a DISCONNECT packet to the server.
        mqttClient.Dispose();
    }

    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)
                .WithTlsOptions(
                    o =>
                    {
                        o.WithCertificateValidationHandler(
                            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 MQTTv5.0.0+.
         */

        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 (!await mqttClient.TryPingAsync())
                            {
                                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));
                        }
                    }
                });

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

    public static async Task ConnectTls_WithCaFile()
    {
        var mqttFactory = new MqttFactory();

        X509Certificate2Collection caChain = new X509Certificate2Collection();
        caChain.ImportFromPem(mosquitto_org); // from https://test.mosquitto.org/ssl/mosquitto.org.crt

        using (var mqttClient = mqttFactory.CreateMqttClient())
        {
            var mqttClientOptions = new MqttClientOptionsBuilder()
                .WithTcpServer("test.mosquitto.org", 8883)
                .WithTlsOptions(new MqttClientTlsOptionsBuilder()
                    .WithTrustChain(caChain) 
                    .Build())
                .Build();

            var connAck = await mqttClient.ConnectAsync(mqttClientOptions);
            Console.WriteLine("Connected to test.moquitto.org:8883 with CaFile mosquitto.org.crt: " + connAck.ResultCode);
        }


    }
    const string mosquitto_org = @"
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
";

}