HiveMQ MQTT Client for .NET

https://hivemq.github.io/hivemq-mqtt-client-dotnet/
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### Complete RawClient workflow

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/rawclient/intro

A full example demonstrating client configuration, event handler setup, connection, subscription, publishing, and cleanup.

```csharp
using HiveMQtt.Client;  

using HiveMQtt.MQTT5.Types;  

  

// Configure the client  

var options = new HiveMQClientOptionsBuilder()  

    .WithBroker("broker.hivemq.com")  

    .WithPort(1883)  

    .WithClientId("raw-client-example")  

    .Build();  

  

var client = new RawClient(options);  

  

// Setup message handler BEFORE connecting  

client.OnMessageReceived += (sender, args) =>  

{  

    Console.WriteLine($"[{args.PublishMessage.Topic}]: {args.PublishMessage.PayloadAsString}");  

};  

  

// Track connection state changes  

client.AfterConnect += (sender, args) => Console.WriteLine("Connected to broker");  

client.AfterDisconnect += (sender, args) => Console.WriteLine("Disconnected from broker");  

  

try  

{  

    // Connect  

    var connectResult = await client.ConnectAsync().ConfigureAwait(false);  

  

    if (connectResult.ReasonCode != ConnAckReasonCode.Success)  

    {  

        Console.WriteLine($"Connection failed: {connectResult.ReasonCode}");  

        return;  

    }  

  

    // Subscribe to topics  

    await client.SubscribeAsync("test/topic1", QualityOfService.AtLeastOnceDelivery).ConfigureAwait(false);  

    await client.SubscribeAsync("test/topic2", QualityOfService.ExactlyOnceDelivery).ConfigureAwait(false);  

  

    // Publish messages  

    for (var i = 0; i < 10; i++)  

    {  

        await client.PublishAsync("test/topic1", $"Message {i}").ConfigureAwait(false);  

        await Task.Delay(100);  

    }  

  

    // Wait for messages  

    await Task.Delay(1000);  

  

    // Disconnect  

    await client.DisconnectAsync().ConfigureAwait(false);  

}  

finally  

{  

    client.Dispose();  

}  
```

--------------------------------

### Quick Start with RawClient

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/rawclient/intro

Demonstrates the basic lifecycle of a RawClient including message handler setup, connection, subscription, publishing, and disconnection.

```csharp
using HiveMQtt.Client;  

using HiveMQtt.MQTT5.Types;  

  

// Create a RawClient  

var client = new RawClient();  

  

// Setup a global message handler BEFORE connecting  

client.OnMessageReceived += (sender, args) =>  

{  

    Console.WriteLine($"Message received on {args.PublishMessage.Topic}: {args.PublishMessage.PayloadAsString}");  

};  

  

// Connect to the broker  

var connectResult = await client.ConnectAsync().ConfigureAwait(false);  

  

// Subscribe to a topic (RawClient does NOT track this subscription)  

await client.SubscribeAsync("my/topic", QualityOfService.AtLeastOnceDelivery).ConfigureAwait(false);  

  

// Publish a message  

await client.PublishAsync("my/topic", "Hello from RawClient!").ConfigureAwait(false);  

  

// Disconnect when done  

await client.DisconnectAsync().ConfigureAwait(false);  

client.Dispose();
```

--------------------------------

### Complete Connection Example

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/connect_options_builder

Demonstrates building connection options and applying them to a client connection.

```csharp
var connectOptions = new ConnectOptionsBuilder()  
    .WithSessionExpiryInterval(3600)  // 1 hour session expiry  
    .WithKeepAlive(60)               // 60 second keep alive  
    .WithCleanStart(true)            // Start with a clean session  
    .Build();  
  
await client.ConnectAsync(connectOptions);
```

--------------------------------

### Minimal MQTT Example

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/quickstart

A simplified example for testing against a local broker using default settings.

```csharp
using HiveMQtt.Client;  

  

// Connect to localhost:1883 with defaults  

var client = new HiveMQClient();  

await client.ConnectAsync();  

  

// Publish a message  

await client.PublishAsync("test/topic", "Hello World!");  

  

// Clean up  

await client.DisconnectAsync();  

client.Dispose();
```

--------------------------------

### Comprehensive SubscribeOptionsBuilder Example

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/subscribing

Demonstrates all available configuration parameters including NoLocal, RetainAsPublished, and RetainHandling.

```csharp
using HiveMQtt.MQTT5.Types;

var options = new SubscribeOptionsBuilder()  

    .WithSubscription(  

        "topic1",                             // Topic  

        QualityOfService.ExactlyOnceDelivery, // Quality of Service Level  

        true,                                 // NoLocal  

        true,                                 // RetainAsPublished  

        RetainHandling.SendAtSubscribe)       // RetainHandling  

    .WithUserProperty("property1", "value1")  

    .WithUserProperties(  

        new Dictionary<string, string> {  

            { "property1", "value1" }, { "property2", "value2" } })  

    .Build();
```

--------------------------------

### Quick Start with HiveMQClient

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/hivemqclient

Demonstrates initializing the client, setting up a message handler, connecting to a broker, subscribing to a topic, and publishing a message.

```csharp
using HiveMQtt.Client;  

using HiveMQtt.MQTT5.Types;  

  

// Create a client  

var client = new HiveMQClient();  

  

// Setup message handler BEFORE subscribing  

client.OnMessageReceived += (sender, args) =>  

{  

    Console.WriteLine($"Message received on {args.PublishMessage.Topic}: {args.PublishMessage.PayloadAsString}");  

};  

  

// Connect to the broker  

var connectResult = await client.ConnectAsync().ConfigureAwait(false);  

  

// Subscribe to a topic (tracked in client.Subscriptions)  

await client.SubscribeAsync("my/topic", QualityOfService.AtLeastOnceDelivery).ConfigureAwait(false);  

  

// Publish a message  

await client.PublishAsync("my/topic", "Hello from HiveMQClient!").ConfigureAwait(false);  

  

// Disconnect when done  

await client.DisconnectAsync().ConfigureAwait(false);  

client.Dispose();
```

--------------------------------

### Start Host and Send Rebirth Command

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/sparkplug/host-application

Starts the host application and publishes a rebirth command to a specific node.

```csharp
await host.StartAsync();  

await host.PublishRebirthCommandAsync("myGroup", "myNode");
```

--------------------------------

### Complete MQTT Workflow Example

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/quickstart

Demonstrates the full lifecycle of configuring, connecting, subscribing, and publishing. Ensure message handlers are defined before subscribing to avoid missing retained messages.

```csharp
using HiveMQtt.Client;  

using HiveMQtt.MQTT5.Types;  

  

// 1. Configure client options  

var options = new HiveMQClientOptionsBuilder()  

    .WithBroker("broker.hivemq.com")  

    .WithPort(1883)  

    .Build();  

  

var client = new HiveMQClient(options);  

  

// 2. Set up message handler BEFORE subscribing  

client.OnMessageReceived += (sender, args) =>  

{  

    Console.WriteLine($"Message Received: {args.PublishMessage.PayloadAsString}");  

};  

  

// 3. Connect to the broker  

var connectResult = await client.ConnectAsync().ConfigureAwait(false);  

  

// 4. Subscribe to topics  

var subscribeOptions = new SubscribeOptionsBuilder()  

    .WithSubscription("topic1", QualityOfService.AtLeastOnceDelivery)  

    .WithSubscription("topic2", QualityOfService.ExactlyOnceDelivery)  

    .Build();  

  

var subscribeResult = await client.SubscribeAsync(subscribeOptions).ConfigureAwait(false);  

  

// 5. Publish a message  

var publishResult = await client.PublishAsync("topic1/example", "Hello, MQTT!").ConfigureAwait(false);  

  

// 6. Disconnect when done  

await client.DisconnectAsync().ConfigureAwait(false);  

client.Dispose();
```

--------------------------------

### WithCleanStart(bool cleanStart)

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/connect_options_builder

Configures whether the connection starts a new session or continues an existing one.

```APIDOC
## WithCleanStart(bool cleanStart)

### Description
Specifies whether the Connection starts a new Session or is a continuation of an existing Session.

### Parameters
- **cleanStart** (bool) - Required - True to start a new session, false to continue an existing one.
```

--------------------------------

### Install HiveMQtt Package

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet

Use the .NET CLI to add the HiveMQtt package to your project.

```bash
dotnet add package HiveMQtt  
```

--------------------------------

### Complete HiveMQClient Implementation

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/hivemqclient

A full example demonstrating client configuration, event handling, connection, subscription management, and message publishing.

```csharp
using HiveMQtt.Client;  

using HiveMQtt.MQTT5.Types;  

  

// Configure the client  

var options = new HiveMQClientOptionsBuilder()  

    .WithBroker("broker.hivemq.com")  

    .WithPort(1883)  

    .WithClientId("hivemqclient-example")  

    .WithAutomaticReconnect(true)  

    .Build();  

  

var client = new HiveMQClient(options);  

  

// Setup global message handler  

client.OnMessageReceived += (sender, args) =>  

{  

    Console.WriteLine($"[{args.PublishMessage.Topic}]: {args.PublishMessage.PayloadAsString}");  

};  

  

// Track connection state changes  

client.AfterConnect += (sender, args) => Console.WriteLine("Connected to broker");  

client.AfterDisconnect += (sender, args) => Console.WriteLine("Disconnected from broker");  

  

try  

{  

    // Connect  

    var connectResult = await client.ConnectAsync().ConfigureAwait(false);  

  

    if (connectResult.ReasonCode != ConnAckReasonCode.Success)  

    {  

        Console.WriteLine($"Connection failed: {connectResult.ReasonCode}");  

        return;  

    }  

  

    // Subscribe with per-subscription callbacks  

    var subscribeOptions = new SubscribeOptionsBuilder()  

        .WithSubscription(  

            new TopicFilter("sensors/temperature", QualityOfService.AtLeastOnceDelivery),  

            (sender, args) => Console.WriteLine($"Temperature: {args.PublishMessage.PayloadAsString}"))  

        .WithSubscription(  

            new TopicFilter("sensors/humidity", QualityOfService.AtLeastOnceDelivery),  

            (sender, args) => Console.WriteLine($"Humidity: {args.PublishMessage.PayloadAsString}"))  

        .Build();  

  

    await client.SubscribeAsync(subscribeOptions).ConfigureAwait(false);  

  

    // View tracked subscriptions  

    Console.WriteLine($"Active subscriptions: {client.Subscriptions.Count}");  

  

    // Publish messages  

    for (var i = 0; i < 10; i++)  

    {  

        await client.PublishAsync("sensors/temperature", $"{20 + i}°C").ConfigureAwait(false);  

        await Task.Delay(100);  

    }  

  

    // Wait for messages  

    await Task.Delay(1000);  

  

    // Unsubscribe by topic  

    await client.UnsubscribeAsync("sensors/temperature").ConfigureAwait(false);  

  

    // Disconnect  

    await client.DisconnectAsync().ConfigureAwait(false);  

}  

finally  

{  

    client.Dispose();  

}
```

--------------------------------

### Trace Level Log Output Example

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/how-to/configure-logging

Example of the verbose output generated when the minlevel is set to Trace, showing packet and event handling activity.

```text
2024-03-14 15:40:18.2252|TRACE|HiveMQtt.Client.HiveMQClient|Trace Level Logging Legend:  
2024-03-14 15:40:18.2312|TRACE|HiveMQtt.Client.HiveMQClient|    -(W)-   == ConnectionWriter  
2024-03-14 15:40:18.2312|TRACE|HiveMQtt.Client.HiveMQClient|    -(PW)-   == ConnectionPublishWriter  
2024-03-14 15:40:18.2312|TRACE|HiveMQtt.Client.HiveMQClient|    -(R)-   == ConnectionReader  
2024-03-14 15:40:18.2312|TRACE|HiveMQtt.Client.HiveMQClient|    -(RPH)- == ReceivedPacketsHandler  
2024-03-14 15:40:18.2320|INFO|HiveMQtt.Client.HiveMQClient|Connecting to broker at 127.0.0.1:1883  
2024-03-14 15:40:18.2343|TRACE|HiveMQtt.Client.HiveMQClient|BeforeConnectEventLauncher  
2024-03-14 15:40:18.2460|TRACE|HiveMQtt.Client.HiveMQClient|Socket connected to 127.0.0.1:1883  
2024-03-14 15:40:18.2464|TRACE|HiveMQtt.Client.HiveMQClient|Queuing packet for send: HiveMQtt.MQTT5.Packets.ConnectPacket  
2024-03-14 15:40:18.2464|TRACE|HiveMQtt.Client.HiveMQClient|-(RPH)- Starting...Connecting  
2024-03-14 15:40:18.2464|TRACE|HiveMQtt.Client.HiveMQClient|-(R)- ConnectionReader Starting...Connecting  
2024-03-14 15:40:18.2464|TRACE|HiveMQtt.Client.HiveMQClient|5: ConnectionMonitor Starting...Connecting  
2024-03-14 15:40:18.2464|TRACE|HiveMQtt.Client.HiveMQClient|-(RPH)- 0 received packets currently waiting to be processed.  
2024-03-14 15:40:18.2464|TRACE|HiveMQtt.Client.HiveMQClient|-(W)- ConnectionWriter Starting...Connecting  
2024-03-14 15:40:18.2464|TRACE|HiveMQtt.Client.HiveMQClient|-(W)- ConnectionWriter: 1 packets waiting to be sent.  
2024-03-14 15:40:18.2476|TRACE|HiveMQtt.Client.HiveMQClient|-(W)- --> Sending ConnectPacket id=0  
2024-03-14 15:40:18.2529|TRACE|HiveMQtt.Client.HiveMQClient|OnConnectSentEventLauncher  
2024-03-14 15:40:18.2529|TRACE|HiveMQtt.Client.HiveMQClient|-(W)- ConnectionWriter: 0 packets waiting to be sent.  
2024-03-14 15:40:18.2732|TRACE|HiveMQtt.Client.HiveMQClient|ReadAsync: Read Buffer Length 11  
2024-03-14 15:40:18.2765|TRACE|HiveMQtt.MQTT5.PacketDecoder|PacketDecoder: Decoded Packet: consumed=11, packet=HiveMQtt.MQTT5.Packets.ConnAckPacket id=0  
2024-03-14 15:40:18.2765|TRACE|HiveMQtt.Client.HiveMQClient|-(R)- <-- Received ConnAckPacket.  Adding to receivedQueue.  
2024-03-14 15:40:18.2765|TRACE|HiveMQtt.Client.HiveMQClient|-(RPH)- <-- Received ConnAck id=0  
2024-03-14 15:40:18.2765|TRACE|HiveMQtt.Client.HiveMQClient|OnConnAckReceivedEventLauncher  
2024-03-14 15:40:18.2775|TRACE|HiveMQtt.Client.HiveMQClient|AfterConnectEventLauncher
```

--------------------------------

### Install HiveMQ MQTT Client via NuGet

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/intro

Use the .NET CLI to add the HiveMQtt package to your project.

```bash
dotnet add package HiveMQtt
```

--------------------------------

### Install HiveMQtt.Sparkplug NuGet package

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/sparkplug/intro

Use the .NET CLI to add the Sparkplug extension package to your project.

```bash
dotnet add package HiveMQtt.Sparkplug
```

--------------------------------

### Example: FireFirstMatchingHandler

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/hivemqclient

Demonstrates the behavior of FireFirstMatchingHandler where only the first matching subscription handler is executed.

```csharp
var options = new HiveMQClientOptionsBuilder()  

    .WithOverlappingSubscriptionBehavior(OverlappingSubscriptionBehavior.FireFirstMatchingHandler)  

    .Build();  

  

var client = new HiveMQClient(options);  

  

// Subscribe to overlapping patterns  

var opts1 = new SubscribeOptions();  

opts1.TopicFilters.Add(new TopicFilter("sensors/#", QualityOfService.AtLeastOnceDelivery));  

opts1.Handlers["sensors/#"] = (s, e) => Console.WriteLine("Wildcard handler");  

await client.SubscribeAsync(opts1);  // First subscription  

  

var opts2 = new SubscribeOptions();  

opts2.TopicFilters.Add(new TopicFilter("sensors/+/temperature", QualityOfService.AtLeastOnceDelivery));  

opts2.Handlers["sensors/+/temperature"] = (s, e) => Console.WriteLine("Specific handler");  

await client.SubscribeAsync(opts2);  // Second subscription  

  

// Global handler always fires regardless of setting  

client.OnMessageReceived += (s, e) => Console.WriteLine("Global handler");  

  

// Publish to sensors/livingroom/temperature  

// Output:  

// Global handler  

// Wildcard handler  

// (Specific handler does NOT fire - only first match fires)  
```

--------------------------------

### Host Application Implementation

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/sparkplug/quickstart

Configure and start a Sparkplug host application to listen for birth messages and publish rebirth commands.

```csharp
var clientOptions = new HiveMQClientOptionsBuilder()

    .WithBroker("localhost")

    .WithPort(1883)

    .WithClientId("my-host")

    .Build();

  

var sparkplugOptions = new SparkplugHostApplicationOptions

{

    SparkplugTopicFilter = "spBv1.0/#",

    UseStateMessages = false

};

  

var host = new SparkplugHostApplication(clientOptions, sparkplugOptions);

host.NodeBirthReceived += (_, e) => Console.WriteLine($"Node birth: {e.Topic.GroupId}/{e.Topic.EdgeNodeId}");

host.DeviceBirthReceived += (_, e) => Console.WriteLine($"Device birth: {e.Topic.DeviceId}");

  

await host.StartAsync();

await host.PublishRebirthCommandAsync("myGroup", "myNode");
```

--------------------------------

### Run HiveMQ Community Edition with Docker

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/intro

Start a local MQTT broker instance using the HiveMQ Community Edition Docker image.

```bash
docker run --name hivemq-ce -d -p 1883:1883 hivemq/hivemq-ce
```

--------------------------------

### Configure Clean Start

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/client_options_builder

Sets whether the broker should discard previous session state upon connection.

```csharp
WithCleanStart(true)
```

--------------------------------

### Set Clean Start

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/connect_options_builder

Determines whether the connection initiates a new session or resumes an existing one.

```csharp
.WithCleanStart(true) // Start with a clean session
```

--------------------------------

### Define Per-Subscription Callbacks

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/subscribing

Shows the method signature for adding a callback to a subscription and provides examples using both lambda expressions and named methods.

```csharp
public SubscribeOptionsBuilder WithSubscription(TopicFilter topicFilter, EventHandler<OnMessageReceivedEventArgs>? handler = null)  
```

```csharp
var builder = new SubscribeOptionsBuilder();  

var options = builder.WithSubscription(  

        new TopicFilter("test/topic", QualityOfService.AtLeastOnceDelivery),  

        (sender, e) =>  

        {  

            Console.WriteLine($"Message received on topic {e.PublishMessage.Topic}: {e.PublishMessage.PayloadAsString}");  

        })  

    .Build();  
```

```csharp
private static void MessageHandler(object? sender, OnMessageReceivedEventArgs eventArgs)  

{  

    Console.WriteLine($"Message Received: {eventArgs.PublishMessage.PayloadAsString}");  

}  

  

var builder = new SubscribeOptionsBuilder();  

var options = builder.WithSubscription(  

        new TopicFilter("test/topic", QualityOfService.AtLeastOnceDelivery),  

        MessageHandler)  

    .Build();  
```

--------------------------------

### Edge Node Implementation

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/sparkplug/quickstart

Configure and start a Sparkplug edge node to handle commands and publish data metrics.

```csharp
var clientOptions = new HiveMQClientOptionsBuilder()

    .WithBroker("localhost")

    .WithPort(1883)

    .WithClientId("my-edge-node")

    .Build();

  

var sparkplugOptions = new SparkplugEdgeNodeOptions

{

    GroupId = "myGroup",

    EdgeNodeId = "myNode"

};

  

var edgeNode = new SparkplugEdgeNode(clientOptions, sparkplugOptions);

edgeNode.NodeCommandReceived += (_, e) => Console.WriteLine($"NCMD: {e.Payload.Metrics.Count} metrics");

  

await edgeNode.StartAsync();

  

var metrics = new[] { SparkplugMetricBuilder.Create("temperature").WithFloatValue(22.5).Build() };

await edgeNode.PublishNodeDataAsync(metrics);
```

--------------------------------

### Configure and Initialize SparkplugHostApplication

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/sparkplug/host-application

Sets up the MQTT client options and Sparkplug host application options required to initialize the host.

```csharp
var clientOptions = new HiveMQClientOptionsBuilder()  

    .WithBroker("localhost")  

    .WithPort(1883)  

    .WithClientId("my-host")  

    .Build();  

  

var sparkplugOptions = new SparkplugHostApplicationOptions  

{  

    SparkplugTopicFilter = "spBv1.0/#",  

    UseStateMessages = false  

};  

  

var host = new SparkplugHostApplication(clientOptions, sparkplugOptions);
```

--------------------------------

### Subscriptions

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/unsubscribe_options

Property to get or set the list of subscriptions for the unsubscribe operation.

```APIDOC
## Property

### Subscriptions

Gets or sets the list of subscriptions for this unsubscribe operation.

### Example
```csharp
options.Subscriptions.Add(new Subscription("home/sensors/temperature", QualityOfService.AtLeastOnce));
```
```

--------------------------------

### Subscribe to Overlapping Topics

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/subscribing

Example of subscribing to multiple overlapping topic patterns.

```csharp
await client.SubscribeAsync("sensors/#");           // Matches: sensors/temperature/livingroom  

await client.SubscribeAsync("sensors/+/temperature"); // Matches: sensors/livingroom/temperature  
```

--------------------------------

### Configure ConnectOptions

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/connect_options

Demonstrates initializing ConnectOptions and overriding default connection settings before establishing a connection.

```csharp
ConnectOptions connectOptions = new ConnectOptions();  

connectOptions.SessionExpiryInterval = 3600;  // 1 hour session expiry  

connectOptions.KeepAlive = 60;                // 60 second keep alive  

connectOptions.CleanStart = true;             // Start with a clean session  

  

await client.ConnectAsync(connectOptions);
```

--------------------------------

### UserProperties

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/unsubscribe_options

Property to get or set custom user properties for the unsubscribe request.

```APIDOC
## Property

### UserProperties

Gets or sets the user properties for the unsubscribe operation.

### Example
```csharp
options.UserProperties["reason"] = "No longer needed";
```
```

--------------------------------

### Initialize Configuration in Startup

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/how-to/client-certificates

Sets up the configuration object within the application startup class.

```csharp
using Microsoft.Extensions.Configuration;  

using System.IO;  

  

// Assuming you are in the Startup.cs or a similar setup file  

public class Startup  

{  

    public IConfiguration Configuration { get; }  

  

    public Startup(IConfiguration configuration)  

    {  

        Configuration = configuration;  

    }  

  

    // Other configurations...  

}
```

--------------------------------

### Async OnMessageReceived Handler

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/how-to/message-ordering

Example of an async void handler where ordering is only guaranteed until the first await statement.

```csharp
client.OnMessageReceived += async (sender, args) =>  

{  

    await SaveToDatabaseAsync(args);  // ordering does NOT extend past the first await  

};
```

--------------------------------

### Configure Proxy with RawClient

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/how-to/configure-proxy

Demonstrates manual proxy configuration using WebProxy for both HiveMQClient and RawClient.

```csharp
using System.Net;  

using HiveMQtt.Client;  

  

var proxy = new WebProxy("http://proxy.example.com:8080");  

  

var options = new HiveMQClientOptionsBuilder()  

    .WithBroker("broker.example.com")  

    .WithProxy(proxy)  

    .Build();  

  

// Works with both HiveMQClient and RawClient  

var rawClient = new RawClient(options);  

await rawClient.ConnectAsync();  
```

--------------------------------

### Connect and Publish with HiveMQtt

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet

Demonstrates initializing a client with builder options, handling incoming messages via events, and performing basic connect, subscribe, and publish operations.

```csharp
using HiveMQtt.Client;  

using HiveMQtt.MQTT5.Types;  

  

// Connect to HiveMQ Cloud (or any MQTT broker)  

var options = new HiveMQClientOptionsBuilder()  

    .WithBroker("your-cluster.hivemq.cloud")  

    .WithPort(8883)  

    .WithUseTls(true)  

    .WithUserName("your-username")  

    .WithPassword("your-password")  

    .Build();  

  

var client = new HiveMQClient(options);  

  

// Handle incoming messages  

client.OnMessageReceived += (sender, args) => {  

    Console.WriteLine($"Received: {args.PublishMessage.PayloadAsString}");  

};  

  

await client.ConnectAsync();  

await client.SubscribeAsync("sensors/temperature");  

await client.PublishAsync("sensors/temperature", "23.5°C");  
```

--------------------------------

### Execute HiveMQtt Benchmarks

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/benchmarks

Run the benchmark suite using the .NET CLI from the project root.

```bash
cd Benchmarks/ClientBenchmarkApp  

dotnet run ClientBenchmarkApp.csproj -c Release  
```

--------------------------------

### Configure Client Certificate from File

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/client_options_builder

Adds a client certificate for authentication by specifying the file path.

```csharp
WithClientCertificate("path/to/certificate.pfx", "password")
```

--------------------------------

### Configure WebSocket Proxy

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/how-to/configure-proxy

Use WithWebSocketProxy for WebSocket connections. This example shows a basic configuration without authentication.

```csharp
using System.Net;  

using HiveMQtt.Client;  

  

// Basic proxy without authentication  

var options = new HiveMQClientOptionsBuilder()  

    .WithWebSocketServer("wss://broker.example.com:8884/mqtt")  

    .WithWebSocketProxy(new WebProxy("http://proxy.example.com:8080"))  

    .Build();  

  

var client = new HiveMQClient(options);  

await client.ConnectAsync();  
```

--------------------------------

### Add Subscription with Options

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/subscribe_options_builder

Configure a subscription with specific QoS, local delivery, and retention settings, optionally including a message handler.

```csharp
SubscribeOptionsBuilder WithSubscription(

    string topic,

    QualityOfService qos,

    bool? noLocal = null,

    bool? retainAsPublished = null,

    RetainHandling? retainHandling = RetainHandling.SendAtSubscribe,

    EventHandler<OnMessageReceivedEventArgs>? messageReceivedHandler = null

);
```

```csharp
builder.WithSubscription(

    "home/sensors/temperature",

    QualityOfService.AtLeastOnce,

    noLocal: true,

    retainAsPublished: false,

    retainHandling: RetainHandling.DoNotSendOnSubscribe,

    messageReceivedHandler: (sender, args) =>

    {

        Console.WriteLine($"Received message: {args.Message.PayloadAsString}");

    });
```

--------------------------------

### Connect with Default Options

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/hivemqclient

Establishes a connection to localhost on port 1883 using default client settings.

```csharp
using HiveMQtt.Client;  

  

var client = new HiveMQClient();  

var connectResult = await client.ConnectAsync().ConfigureAwait(false);  


```

--------------------------------

### Constructing and Publishing an MQTT5 Message

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/publishing

Demonstrates how to instantiate an MQTT5PublishMessage, configure properties like Retain and UserProperties, and send it using PublishAsync.

```csharp
var message = new MQTT5PublishMessage  

{  

    Topic = "topic1/example",  

    Payload = Encoding.UTF8.GetBytes("Hello, World!"),  

    QoS = QualityOfService.AtLeastOnceDelivery,  

};  

  

message.Retain = true;  

message.UserProperties.Add("Client-Geo", "-33.8688, 151.2093");  

  

var result = await client.PublishAsync(message);
```

--------------------------------

### Connect with default settings

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/connecting

Establishes a connection to a local broker on localhost port 1883 without additional configuration.

```csharp
using HiveMQtt.Client;  

  

// Connect  

var client = new HiveMQClient();  

var connectResult = await client.ConnectAsync().ConfigureAwait(false);
```

--------------------------------

### Configure Proxy via Environment Variables

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/how-to/configure-proxy

Shows how to retrieve proxy settings from environment variables to avoid hardcoding credentials.

```csharp
using System.Net;  

using HiveMQtt.Client;  

  

var proxyUrl = Environment.GetEnvironmentVariable("HTTP_PROXY");  

var builder = new HiveMQClientOptionsBuilder()  

    .WithBroker("broker.example.com")  

    .WithPort(1883);  

  

if (!string.IsNullOrEmpty(proxyUrl))  

{  

    var proxy = new WebProxy(proxyUrl);  

      

    // Optional: Add credentials from environment  

    var proxyUser = Environment.GetEnvironmentVariable("PROXY_USER");  

    var proxyPass = Environment.GetEnvironmentVariable("PROXY_PASS");  

      

    if (!string.IsNullOrEmpty(proxyUser))  

    {  

        proxy.Credentials = new NetworkCredential(proxyUser, proxyPass);  

    }  

      

    builder.WithProxy(proxy);  

}  

  

var options = builder.Build();  

var client = new HiveMQClient(options);  
```

--------------------------------

### Initialize MQTT5PublishMessage

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/publish_message

Constructors for creating a new publish message instance.

```csharp
MQTT5PublishMessage();
```

```csharp
var message = new MQTT5PublishMessage();
```

```csharp
MQTT5PublishMessage(string topic, QualityOfService? qos);
```

```csharp
var message = new MQTT5PublishMessage("home/sensors/temperature", QualityOfService.AtLeastOnce);
```

--------------------------------

### Connect with Basic Credentials

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/how-to/connect-with-auth

Establishes a TLS-secured connection to an MQTT broker using hardcoded credentials.

```csharp
using HiveMQtt.Client;  

using HiveMQtt.MQTT5.ReasonCodes;  

  

var options = new HiveMQClientOptionsBuilder()  

    .WithBroker("your-broker.hivemq.cloud")  

    .WithPort(8883)  

    .WithUseTls(true)  

    .WithUserName("my-username")  

    .WithPassword("my-password")  

    .Build();  

  

var client = new HiveMQClient(options);  

var connectResult = await client.ConnectAsync().ConfigureAwait(false);  

  

if (connectResult.ReasonCode == ConnAckReasonCode.Success)  

{  

    Console.WriteLine("Connected successfully!");  

}  
```

--------------------------------

### Migrate from Plain String to SecureString

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/security

Demonstrates the transition from obsolete plain string methods to SecureString to avoid compiler warnings.

```csharp

// ⚠️ This generates a compiler warning  

var options = new HiveMQClientOptionsBuilder()  

    .WithPassword("plain-text-password")  // CS0618: Obsolete warning  

    .Build();  

  

// ✅ Use SecureString instead  

var options = new HiveMQClientOptionsBuilder()  

    .WithPassword(securePassword)  

    .Build();  



```

--------------------------------

### Build()

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/last_will_and_testament_builder

Constructs the LastWillAndTestament instance and validates the configuration.

```APIDOC
## Build()

### Description
Constructs the LastWillAndTestament instance and validates the configuration.

### Example
var lwt = builder.WithTopic("client/disconnect").WithPayload("Disconnected unexpectedly").WithQualityOfServiceLevel(QualityOfService.ExactlyOnce).WithRetain(true).Build();
```

--------------------------------

### Connect with Specific Options

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/hivemqclient

Configures client connection parameters such as broker address, port, TLS, and client ID using the builder pattern.

```csharp
var options = new HiveMQClientOptionsBuilder()  

    .WithBroker("broker.hivemq.com")  

    .WithPort(8883)  

    .WithUseTls(true)  

    .WithClientId("my-client-id")  

    .Build();  

  

var client = new HiveMQClient(options);  

var connectResult = await client.ConnectAsync().ConfigureAwait(false);  


```

--------------------------------

### Basic Publishing and Subscribing

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/namespaces

Standard pattern for connecting, subscribing to a topic, and publishing a message.

```csharp
using HiveMQtt.Client;  

using HiveMQtt.MQTT5.Types;  

  

var client = new HiveMQClient();  

await client.ConnectAsync();  

await client.SubscribeAsync("topic", QualityOfService.AtLeastOnceDelivery);  

await client.PublishAsync("topic", "Hello!");  
```

--------------------------------

### Instantiate X509Certificate2 with Password

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/how-to/client-certificates

Manually create an X509Certificate2 object with a password before passing it to the builder.

```csharp
using HiveMQtt.Client;  

using System.Security.Cryptography.X509Certificates;  

  

var clientCertificate = new X509Certificate2(  

    "path/to/certificate-with-password.pem",  

    "certificate-password");  

  

var options = new HiveMQClientOptionsBuilder()  

    .WithClientCertificate(clientCertificate)  

    .Build();  

  

var client = new HiveMQClient(options);
```

--------------------------------

### Build()

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/connect_options_builder

Constructs and returns the final ConnectOptions instance based on the configured settings.

```APIDOC
## Build()

### Description
Creates and returns a new ConnectOptions object with all the configured settings.

### Returns
- **ConnectOptions** - The configured options object.
```

--------------------------------

### WithSubscription(string, QualityOfService, bool?, bool?, RetainHandling?, EventHandler?)

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/subscribe_options_builder

Adds a subscription with detailed options including topic, QoS, and specific MQTT subscription flags.

```APIDOC
## WithSubscription(string topic, QualityOfService qos, bool? noLocal, bool? retainAsPublished, RetainHandling? retainHandling, EventHandler? messageReceivedHandler)

### Description
Adds a subscription with detailed options.

### Parameters
- **topic** (string) - Required - The topic name.
- **qos** (QualityOfService) - Required - The QoS level.
- **noLocal** (bool?) - Optional - Indicates whether this client receives messages it publishes.
- **retainAsPublished** (bool?) - Optional - Determines if the retain flag remains as published.
- **retainHandling** (RetainHandling?) - Optional - Defines how retained messages are handled.
- **messageReceivedHandler** (EventHandler?) - Optional - A handler for messages received on this subscription.
```

--------------------------------

### Configure DisconnectOptions

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/disconnect_options

Demonstrates initializing DisconnectOptions and setting various properties before passing them to the DisconnectAsync method.

```csharp
DisconnectOptions disconnectOptions = new DisconnectOptions();  

disconnectOptions.ReasonCode = DisconnectReasonCode.NormalDisconnection;  

disconnectOptions.SessionExpiry = 3600;  

disconnectOptions.ReasonString = "Device power save mode";  

disconnectOptions.UserProperties = new Dictionary<string, string> { { "device-id", "xrw02k-224a" }, { "TZ", "CEST" } };  

  

await client.DisconnectAsync(disconnectOptions);
```

--------------------------------

### Simple Topic Subscription

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/hivemqclient

Demonstrates subscribing to topics with default or specific Quality of Service (QoS) levels and additional MQTT 5.0 subscription options.

```csharp
// Subscribe with default options (QoS 0)  

await client.SubscribeAsync("my/topic").ConfigureAwait(false);  

  

// Subscribe with specific QoS  

await client.SubscribeAsync("my/topic", QualityOfService.AtLeastOnceDelivery).ConfigureAwait(false);  

  

// Subscribe with additional options  

await client.SubscribeAsync(  

    "my/topic",  

    QualityOfService.ExactlyOnceDelivery,  

    noLocal: true,  

    retainAsPublished: true,  

    retainHandling: RetainHandling.SendAtSubscribe  

).ConfigureAwait(false);
```

--------------------------------

### Configure Credentials via appsettings.json

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/how-to/connect-with-auth

Reads MQTT configuration settings from a standard .NET configuration section.

```csharp
// In appsettings.json:  

// {  

//   "Mqtt": {  

//     "Broker": "your-broker.hivemq.cloud",  

//     "Username": "your-username",  

//     "Password": "your-password"  

//   }  

// }  

  

var mqttConfig = configuration.GetSection("Mqtt");  

var options = new HiveMQClientOptionsBuilder()  

    .WithBroker(mqttConfig["Broker"])  

    .WithPort(8883)  

    .WithUseTls(true)  

    .WithUserName(mqttConfig["Username"])  

    .WithPassword(mqttConfig["Password"])  

    .Build();  
```

--------------------------------

### Initialize SubscribeOptionsBuilder

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/subscribe_options_builder

Instantiate the builder to begin configuring subscription options.

```csharp
SubscribeOptionsBuilder();
```

```csharp
var builder = new SubscribeOptionsBuilder();
```

--------------------------------

### Enable Detailed Logging

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/help

Configure NLog to output TRACE level logs for troubleshooting purposes.

```text
// Add NLog.config to your project with TRACE level
```

--------------------------------

### Build ConnectOptions

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/connect_options_builder

Constructs a new ConnectOptions instance using the configured builder settings.

```csharp
ConnectOptions options = new ConnectOptionsBuilder()  
    .WithSessionExpiryInterval(3600)  
    .WithKeepAlive(60)  
    .WithCleanStart(true)  
    .Build();
```

--------------------------------

### Acknowledge by Event Args

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/how-to/manual-ack

Recommended approach for mixed QoS subscriptions; it safely handles QoS 0 (no-op) and QoS 1/2 messages.

```csharp
client.OnMessageReceived += async (sender, args) =>  

{  

    // Process the message (e.g. persist, forward)...  

    await ProcessMessageAsync(args.PublishMessage);  

  

    // Safe for any QoS: no-op for QoS 0, sends PubAck/PubRec for QoS 1/2  

    await client.AckAsync(args);  

};
```

--------------------------------

### Initialize LastWillAndTestament with binary payload

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/last_will_and_testament

Creates a new instance using a byte array for the payload.

```csharp
LastWillAndTestament(string topic, byte[] payload, QualityOfService qos = QualityOfService.AtMostOnceDelivery, bool retain = false);
```

```csharp
var lwt = new LastWillAndTestament("disconnect/topic", Encoding.UTF8.GetBytes("Client disconnected"), QualityOfService.ExactlyOnce, true);
```

--------------------------------

### Build LastWillAndTestament instance

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/last_will_and_testament_builder

Constructs the LastWillAndTestament instance and validates the configuration.

```csharp
LastWillAndTestament Build();
```

```csharp
var lwt = builder  

    .WithTopic("client/disconnect")  

    .WithPayload("Disconnected unexpectedly")  

    .WithQualityOfServiceLevel(QualityOfService.ExactlyOnce)  

    .WithRetain(true)  

    .Build();
```

--------------------------------

### Configure Proxy via appsettings.json

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/how-to/configure-proxy

Provides the JSON configuration structure and the C# code to load proxy settings from an appsettings.json file.

```json
{
  "MqttSettings": {
    "Broker": "broker.example.com",
    "Port": 1883,
    "Proxy": {
      "Enabled": true,
      "Url": "http://proxy.example.com:8080",
      "Username": "",
      "Password": ""
    }
  }
}
```

```csharp
using System.Net;  

using HiveMQtt.Client;  

using Microsoft.Extensions.Configuration;  

  

var config = new ConfigurationBuilder()  

    .AddJsonFile("appsettings.json")  

    .Build();  

  

var mqttSettings = config.GetSection("MqttSettings");  

var builder = new HiveMQClientOptionsBuilder()  

    .WithBroker(mqttSettings["Broker"])  

    .WithPort(int.Parse(mqttSettings["Port"]));  

  

var proxySection = mqttSettings.GetSection("Proxy");  

if (proxySection.GetValue<bool>("Enabled"))  

{  

    var proxy = new WebProxy(proxySection["Url"]);  

      

    var username = proxySection["Username"];  

    if (!string.IsNullOrEmpty(username))  

    {  

        proxy.Credentials = new NetworkCredential(  

            username,   

            proxySection["Password"]);  

    }  

      

    builder.WithProxy(proxy);  

}  

  

var options = builder.Build();  
```

--------------------------------

### MQTT5PublishMessage Constructors

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/publish_message

Initializes a new instance of the MQTT5PublishMessage class.

```APIDOC
## MQTT5PublishMessage()

### Description
Initializes a new instance of the MQTT5PublishMessage class.

## MQTT5PublishMessage(string topic, QualityOfService? qos)

### Description
Initializes a new instance of the MQTT5PublishMessage class with the specified topic and Quality of Service level.

### Parameters
- **topic** (string) - Required - The topic name.
- **qos** (QualityOfService?) - Required - The QoS level.
```

--------------------------------

### Build()

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/subscribe_options_builder

Constructs the SubscribeOptions instance and validates the configuration.

```APIDOC
## Build()

### Description
Constructs the `SubscribeOptions` instance and validates the configuration.
```

--------------------------------

### Initialize UnsubscribeOptions

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/unsubscribe_options

Create a new instance of the UnsubscribeOptions class.

```csharp
UnsubscribeOptions();
```

```csharp
var options = new UnsubscribeOptions();
```

--------------------------------

### Initialize SubscribeOptions

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/subscribe_options

Create a new instance of the SubscribeOptions class.

```csharp
SubscribeOptions();
```

```csharp
var options = new SubscribeOptions();
```

--------------------------------

### Build()

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/client_options_builder

Builds the HiveMQClientOptions instance based on the configured options.

```APIDOC
### Build()

Builds the HiveMQClientOptions instance based on the configured options.

**Example:**
`HiveMQClientOptions options = new HiveMQClientOptionsBuilder().WithBroker("mqtt.example.com").WithPort(1883).Build();`
```

--------------------------------

### Define Certificate Configuration Model

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/how-to/client-certificates

Creates a C# class to map the certificate settings from the configuration file.

```csharp
public class CertificateSettings  

{  

    public string CertificatePath { get; set; }  

    public string CertificatePassword { get; set; }  

}
```

--------------------------------

### Build HiveMQClientOptions

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/client_options_builder

Finalizes the configuration and builds the HiveMQClientOptions instance.

```csharp
HiveMQClientOptions options = new HiveMQClientOptionsBuilder().WithBroker("mqtt.example.com").WithPort(1883).Build();
```

--------------------------------

### Build SubscribeOptions

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/subscribe_options_builder

Finalize the configuration and generate the SubscribeOptions instance.

```csharp
SubscribeOptions Build();
```

```csharp
var options = builder

    .WithSubscription("home/sensors/temperature", QualityOfService.AtLeastOnce)

    .WithUserProperty("key", "value")

    .Build();



options.Validate();
```

--------------------------------

### Build()

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/unsubscribe_options_builder

Constructs the UnsubscribeOptions instance based on the provided settings.

```APIDOC
## Build()

### Description
Validates the builder configuration and creates an instance of `UnsubscribeOptions`.

### Example
```csharp
var options = builder
    .WithSubscription(new Subscription("home/sensors/temperature", QualityOfService.AtLeastOnce))
    .WithUserProperty("reason", "No longer needed")
    .Build();
```
```

--------------------------------

### Configure Credentials via Environment Variables

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/how-to/connect-with-auth

Retrieves broker and authentication details from system environment variables to avoid hardcoding sensitive data.

```csharp
var options = new HiveMQClientOptionsBuilder()  

    .WithBroker(Environment.GetEnvironmentVariable("MQTT_BROKER"))  

    .WithPort(8883)  

    .WithUseTls(true)  

    .WithUserName(Environment.GetEnvironmentVariable("MQTT_USERNAME"))  

    .WithPassword(Environment.GetEnvironmentVariable("MQTT_PASSWORD"))  

    .Build();  
```

--------------------------------

### LastWillAndTestamentBuilder()

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/last_will_and_testament_builder

Initializes a new instance of the LastWillAndTestamentBuilder class.

```APIDOC
## LastWillAndTestamentBuilder()

### Description
Initializes a new instance of the LastWillAndTestamentBuilder class.

### Signature
`LastWillAndTestamentBuilder()`
```

--------------------------------

### Configure Multiple Client Certificates

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/client_options_builder

Adds a list of X.509 certificates for client authentication.

```csharp
WithClientCertificates(new List<X509Certificate2> { new X509Certificate2("path/to/certificate1.pfx", "password"), new X509Certificate2("path/to/certificate2.pfx", "password") })
```

--------------------------------

### Subscribe to a topic with QoS

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/subscribing

Specify a QualityOfService level when subscribing to a topic.

```csharp
using HiveMQtt.MQTT5.Types; // For QualityOfService enum  

  

string topic = "my/topic";  

QualityOfService qos = QualityOfService.AtLeastOnceDelivery;  

  

await client.SubscribeAsync(topic, qos).ConfigureAwait(false);  
```

--------------------------------

### Performance Optimization for QoS 0

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/rawclient/intro

Leverage the fast path for QoS 0 messages by omitting topic aliases and retain flags to minimize validation overhead.

```csharp
// This takes the fast path - minimal overhead  

var message = new MQTT5PublishMessage  

{  

    Topic = "sensor/data",  

    Payload = sensorData,  

    QoS = QualityOfService.AtMostOnceDelivery,  

};  

  

var result = await client.PublishAsync(message).ConfigureAwait(false);
```

--------------------------------

### LastWillAndTestament(string topic, byte[] payload, QualityOfService qos, bool retain)

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/last_will_and_testament

Initializes a new instance of the LastWillAndTestament class with a binary payload.

```APIDOC
## Constructor: LastWillAndTestament(string topic, byte[] payload, QualityOfService qos = QualityOfService.AtMostOnceDelivery, bool retain = false)

### Description
Initializes a new instance of the LastWillAndTestament class with a binary payload.

### Parameters
- **topic** (string) - Required - The topic of the message.
- **payload** (byte[]) - Required - The payload in binary format.
- **qos** (QualityOfService) - Optional - The QoS level (default: AtMostOnceDelivery).
- **retain** (bool) - Optional - Whether the message should be retained by the broker.

### Example
```csharp
var lwt = new LastWillAndTestament("disconnect/topic", Encoding.UTF8.GetBytes("Client disconnected"), QualityOfService.ExactlyOnce, true);
```
```

--------------------------------

### Initialize LastWillAndTestament with string payload

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/last_will_and_testament

Creates a new instance using a UTF-8 encoded string payload.

```csharp
LastWillAndTestament(string topic, string payload, QualityOfService qos = QualityOfService.AtMostOnceDelivery, bool retain = false);
```

```csharp
var lwt = new LastWillAndTestament("disconnect/topic", "Client disconnected", QualityOfService.AtLeastOnce, true);
```

--------------------------------

### Initialize LastWillAndTestamentBuilder

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/last_will_and_testament_builder

Instantiate the builder to begin configuring a Last Will and Testament message.

```csharp
LastWillAndTestamentBuilder();
```

```csharp
var builder = new LastWillAndTestamentBuilder();
```

--------------------------------

### Configure Certificate Settings in appsettings.json

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/how-to/client-certificates

Defines the structure for certificate paths and passwords within a JSON configuration file.

```json
{
  // Other configuration settings
  "CertificateSettings": {
    "CertificatePath": "path/to/certificate-with-password.pem",
    "CertificatePassword": "YourSecurePassword"
  }
}
```

--------------------------------

### Initialize UnsubscribeOptionsBuilder

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/unsubscribe_options_builder

Constructor for creating a new instance of the builder.

```csharp
UnsubscribeOptionsBuilder();
```

```csharp
var builder = new UnsubscribeOptionsBuilder();
```

--------------------------------

### Configure Client Certificate

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/reference/client_options_builder

Adds an X.509 certificate for client authentication.

```csharp
WithClientCertificate(new X509Certificate2("path/to/certificate.pfx", "password"))
```

--------------------------------

### Build and Execute Subscription

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/subscribing

Finalize the options object and pass it to the client's SubscribeAsync method.

```csharp
var options = builder.Build();
```

```csharp
await client.SubscribeAsync(options);
```

--------------------------------

### Configure Multiple Certificates

Source: https://hivemq.github.io/hivemq-mqtt-client-dotnet/docs/hivemqtt/security

Chain multiple certificates by calling WithClientCertificate multiple times.

```csharp
var options = new HiveMQClientOptionsBuilder()  

    .WithBroker("your-broker.hivemq.cloud")  

    .WithPort(8883)  

    .WithUseTls(true)  

    .WithClientCertificate("path/to/client-cert.pem")  

    .WithClientCertificate("path/to/intermediate-ca.pem")  

    .Build();
```
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