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HiveMQtt 0.44.0

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The Spectacular C# MQTT and Sparkplug Clients for .NET

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Looking for the Sparkplug Client? Use HiveMQtt.Sparkplug and start with the for quick start guides and examples.

💽 Installation & Compatibility

• Easy-to-Install: Available as a NuGet package.
• Globally Compatible: Built to be a fully compliant MQTT 5.0 client compatible with all modern MQTT brokers.
• Multi-Targeted: Supports .NET 6.0, 7.0, 8.0, 9.0 & 10.0
• Sparkplug Client extension: The HiveMQtt.Sparkplug package adds Host Application and Edge Node support for industrial IoT (IIoT) using the Eclipse Sparkplug B 3.0 specification—install with dotnet add package HiveMQtt.Sparkplug and see the for full details.

🚀 Features

• MQTT 5.0 Support: Fully compliant with the latest MQTT 5.0 specification, ensuring compatibility with modern MQTT brokers.
• Multiple Transport Options: Support for both TCP and WebSocket connections (ws:// and wss://), ideal for network environments that restrict TCP traffic or require HTTP-compatible transport.
• Manual Acknowledgement: Control when the broker considers QoS 1 and QoS 2 messages delivered. Process or persist messages first, then call AckAsync—ideal for at-least-once and exactly-once workflows. See the manual ack guide.
• TCP & WebSocket Proxy Support: Connect through HTTP proxies—TCP via HTTP CONNECT tunneling (WithProxy), WebSocket via WithWebSocketProxy. Perfect for corporate networks and firewalls.
• Back Pressure Management: Automatically manages back pressure to prevent overwhelming the broker (or client), ensuring reliable and efficient communication.
• Asynchronous Design: Designed for high-performance and low-latency communication, allowing your application to process multiple messages concurrently.
• Extensive Event System: Hook into all parts of the client down to the packet level with built in events.
• Global and Per-Subscription Message Handling: Use multiple targeted handlers for more targeted and specialized message processing.
• Full Last Will & Testament Support: Reliable message delivery and notification of client disconnections.
• Secure Client Identification: Full support for X.509 client certificates and TLS connections.
• Observable: Configure up to TRACE level logging for package internals.
• Fast: Optimized & benchmarked. See the benchmark results here.

🔒 Security

• Secure Password Storage: Passwords are stored using SecureString to prevent exposure in memory dumps and process memory. Use WithPassword(SecureString) for enhanced security.
• Secure Certificate Password Handling: Certificate passwords are handled securely using SecureString. Use WithClientCertificate(path, SecureString) for enhanced security.
• Memory-Safe Password Handling: Temporary password strings are automatically cleared from memory after use, ensuring no sensitive data persists in memory.
• Backward Compatibility: Existing code using string passwords continues to work while being automatically converted to secure storage internally.
• TLS/SSL Support: Full support for encrypted connections (both TCP and WebSocket) with configurable certificate validation and custom certificate handling.
• Secure WebSocket (wss://): Complete support for secure WebSocket connections with client certificate authentication and configurable certificate validation.
• X.509 Certificate Authentication: Complete support for client certificate authentication with secure private key handling for both TCP and WebSocket connections.

🏝️ Ease of Use

• Easy to Use: Smart defaults, excellent interfaces and intelligent automation make implementation a breeze.
• Easy Integration: Simple and intuitive API makes it easy to integrate with your .NET applications.

🛟 Maintenance and Support

• Actively Maintained: Built by the MQTT professionals that built HiveMQ (and do this for a living).
• Supported: Contact us anytime in this repository, in the community forum or through support.
• Extensively Documented: What good is it without excellent documentation?

🐧 Open Source

• Open Source: No blackbox code. Only trusted, tested and reviewed open source code.

📍 Get Started Today

Download the HiveMQ C# MQTT Client for .NET and start building your next-generation IoT, industrial automation, or real-time data streaming application with HiveMQ on your side.

Do you have a success story with this client? Let us know. We'd love to feature your story in a blog post or video and you'll get some sweet HiveMQ swag (and publicity) along the way.

What is this?

MQTT is an open standard protocol for publishing and consuming messages from IoT devices all the way up to mainframes. It's binary, massively performant and easy to use.

This client library is used to publish and consume messages over MQTT. So you can get the temperature from a remote sensor, send a control message to a factory robot, tunnel WhatsApp messages to an X account or anything else you can imagine.

This is the client library that speaks with an MQTT broker that delivers messages to their final destination.

Need a broker? Sign up for a free broker at HiveMQ Cloud and be up and running in a couple minutes. Connect up to 100 devices - no credit card required.

MQTT Resources

• MQTT Essentials (Great for beginners wanting an introduction)
• MQTT Toolbox
• MQTT Client Library Encyclopedia
• HiveMQ Public Broker
• HiveMQ Support

Need an MQTT Broker?

This client communicates with an MQTT broker to publish and consume messages. It's built to be compatible with all major MQTT brokers but if you need a broker now run the HiveMQ Community Edition:

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

This will run the HiveMQ Community Edition broker on localhost port 1883.

If you need advanced features, check out our premium editions or alternatively HiveMQ Cloud which is free to connect up to 100 devices (no credit card required).

Install

HiveMQtt (core client)

This package is available on NuGet.org and can be installed with:

dotnet add package HiveMQtt

See the HiveMQtt NuGet page for more installation options.

HiveMQtt.Sparkplug (Sparkplug B extension)

The HiveMQtt.Sparkplug package is now available on NuGet. It extends the HiveMQtt client with Sparkplug B 3.0 support for industrial IoT: Host Applications (subscribe to Edge Nodes and Devices, publish NCMD/DCMD) and Edge Nodes (publish NBIRTH/NDATA/NDEATH, DBIRTH/DDATA/DDEATH; receive NCMD/DCMD). Install with:

dotnet add package HiveMQtt.Sparkplug

See the HiveMQtt.Sparkplug NuGet page and the for details and quick start.

Example

The following illustrates the client pattern to connect, subscribe and publish messages.

using HiveMQtt.Client;
using HiveMQtt.MQTT5.Types;

// Setup Client options and instantiate
var options = new HiveMQClientOptionsBuilder().
 WithBroker("candy.x39.eu.hivemq.cloud").
 WithPort(8883).
 WithUseTls(true).
 Build();
var client = new HiveMQClient(options);

// Setup application message handlers BEFORE subscribing to a topic
client.OnMessageReceived += (sender, args) =>
{
 Console.WriteLine($"Message Received: {args.PublishMessage.PayloadAsString}");
};

// Connect to the MQTT broker
var connectResult = await client.ConnectAsync().ConfigureAwait(false);

// Configure the subscriptions we want and subscribe
var builder = new SubscribeOptionsBuilder();
builder.WithSubscription("topic1", QualityOfService.AtLeastOnceDelivery)
 .WithSubscription("topic2", QualityOfService.ExactlyOnceDelivery);
var subscribeOptions = builder.Build();
var subscribeResult = await client.SubscribeAsync(subscribeOptions);

// Publish a message
var publishResult = await client.PublishAsync("topic1/example", "Hello Payload");

WebSocket Connection Example

The client also supports WebSocket connections (ws:// and wss://). WebSocket is useful when:

• Network policies only allow HTTP/HTTPS traffic (firewalls, proxies that block TCP)
• You need to leverage existing WebSocket infrastructure
• You're building server-side .NET applications that require HTTP-compatible transport

using HiveMQtt.Client;
using HiveMQtt.MQTT5.Types;

// Connect via WebSocket (ws://)
var options = new HiveMQClientOptionsBuilder()
 .WithWebSocketServer("ws://localhost:8000/mqtt")
 .WithClientId("WebSocketClient")
 .Build();

// Or connect via secure WebSocket (wss://) with TLS
var secureOptions = new HiveMQClientOptionsBuilder()
 .WithWebSocketServer("wss://broker.hivemq.com:8884/mqtt")
 .WithClientId("SecureWebSocketClient")
 .Build();

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

// Use the same API for publish/subscribe - works identically to TCP connections
client.OnMessageReceived += (sender, args) =>
{
 Console.WriteLine($"WebSocket Message: {args.PublishMessage.PayloadAsString}");
};

await client.SubscribeAsync("my/topic");
await client.PublishAsync("my/topic", "Hello from WebSocket!");

Manual Acknowledgement (QoS 1 & 2)

When you need to process or persist messages before the broker is told they were received, enable manual ack. The client won't send PubAck/PubRec until you call AckAsync:

using HiveMQtt.Client;
using HiveMQtt.MQTT5.Types;

var options = new HiveMQClientOptionsBuilder()
 .WithBroker("broker.example.com")
 .WithPort(1883)
 .WithManualAck()
 .Build();

var client = new HiveMQClient(options);
client.OnMessageReceived += async (sender, args) =>
{
 await ProcessOrPersistAsync(args.PublishMessage);
 await client.AckAsync(args); // Safe for any QoS (no-op for QoS 0)
};

await client.ConnectAsync();
await client.SubscribeAsync("orders/#", QualityOfService.AtLeastOnceDelivery);

See the manual acknowledgement guide for Receive Maximum, thread safety, and RawClient usage.

TCP and WebSocket Proxy Support

Connect through HTTP proxies—essential in corporate or restricted networks:

TCP (HTTP CONNECT tunnel):

using System.Net;
using HiveMQtt.Client;

var options = new HiveMQClientOptionsBuilder()
 .WithBroker("broker.example.com")
 .WithPort(1883)
 .WithProxy(new WebProxy("http://proxy.example.com:8080"))
 .Build();

var client = new HiveMQClient(options);
await client.ConnectAsync();

WebSocket: Use WithWebSocketProxy(new WebProxy("http://proxy.example.com:8080")) with WithWebSocketServer(...). Both support proxy credentials. Full details: Configure a Proxy Server.

For a Quickstart, more examples and walkthroughs, see the documentation.

Other MQTT Clients

• Java
• Javascript

For a list of all known MQTT clients, see MQTT.org.

🛡 License

👁 License

This project is licensed under the terms of the Apache Software License 2.0 license. See LICENSE for more details.

📃 Citation

@misc{hivemq-mqtt-client-dotnet,
 author = {HiveMQ GmbH},
 title = {The HiveMQ C# MQTT client for .NET},
 year = {2026},
 publisher = {GitHub},
 journal = {GitHub repository},
 howpublished = {\url{https://github.com/hivemq/hivemq-mqtt-client-dotnet}}
}