Introduction to MQTT and Go

When it comes to the Internet of Things (IoT) and smart home projects, efficient communication between devices is crucial. MQTT (Message Queuing Telemetry Transport) is a lightweight messaging protocol that fits the bill perfectly. In this article, we’ll delve into developing a high-performance MQTT broker using Go, a language known for its simplicity, performance, and concurrency features.

Why Choose Go for MQTT Broker Development?

Go, or Golang, is an excellent choice for building high-performance applications due to its:

  • Concurrency Support: Go’s goroutines and channels make it easy to handle multiple connections concurrently, which is essential for an MQTT broker.
  • Performance: Go is compiled to machine code, making it fast and efficient.
  • Simplicity: Go’s clean syntax and minimalistic approach make it easier to write and maintain code.

Choosing the Right MQTT Broker

There are several MQTT brokers written in Go that you can use or extend. Here, we’ll focus on two popular ones: Comqtt and Mochi MQTT.

Comqtt

Comqtt is an embeddable high-performance MQTT broker server that supports MQTT v3.0, v3.1.1, and v5.0. Here are some key features:

  • Distributed Cluster Support: Comqtt can be used in a distributed cluster setup.
  • High Performance: Its message throughput is comparable to other popular brokers like Mosquitto, Mosca, and VerneMQ.
  • Ease of Use: Comqtt is designed to be clean, easy to read, customize, and extend[1].

Mochi MQTT

Mochi MQTT is another fully compliant, embeddable high-performance MQTT broker server. It supports MQTT v3.0, v3.1.1, and v5.0, with features such as:

  • Full MQTTv5 Feature Compliance: Includes features like topic aliases, shared subscriptions, and message expiry.
  • Developer-Centric: Most core broker code is exported and accessible, allowing for total developer control[3][5].

Setting Up the MQTT Broker

Let’s walk through setting up both Comqtt and Mochi MQTT as standalone brokers.

Setting Up Comqtt

To run Comqtt as a standalone broker:

cd cmd
go build -o comqtt ./single/main.go
./comqtt

Or, if you want to use a configuration file:

./comqtt --conf=./config/single.yml

This will expose TCP, WebSocket, and dashboard listeners[1].

Setting Up Mochi MQTT

To run Mochi MQTT as a standalone broker:

cd cmd
go build -o mqtt && ./mqtt

This command will also expose TCP, WebSocket, and dashboard listeners[3].

Step-by-Step Guide to Running the Broker

Here’s a detailed step-by-step guide to running Mochi MQTT, but the process is similar for Comqtt.

Step 1: Checkout the Repository

First, you need to clone the repository:

git clone https://github.com/mochi-mqtt/server.git
cd server

Step 2: Build the Broker

Navigate to the cmd directory and build the broker:

cd cmd
go build -o mqtt && ./mqtt

Step 3: Configure the Broker

You can configure the broker using a configuration file or by modifying the code directly. Here’s an example of how to create and add a TCP listener in code:

import (
    "github.com/mochi-co/mqtt/server"
    "github.com/mochi-co/mqtt/server/listeners"
    "log"
)

func main() {
    // Create the new MQTT Server.
    server := server.NewServer(nil)

    // Create a TCP listener on a standard port.
    tcp := listeners.NewTCP("t1", ":1883")

    // Add the listener to the server with default options (nil).
    err := server.AddListener(tcp, nil)
    if err != nil {
        log.Fatal(err)
    }

    // Start the broker. Serve() is blocking - see examples folder for usage ideas.
    err = server.Serve()
    if err != nil {
        log.Fatal(err)
    }
}

Understanding MQTT Broker Architecture

Here’s a high-level overview of the MQTT broker architecture using a sequence diagram:

sequenceDiagram participant Client participant Broker participant Subscriber Note over Client,Broker: Client connects to Broker Client->>Broker: CONNECT Broker->>Client: CONNACK Note over Client,Broker: Client publishes message Client->>Broker: PUBLISH (topic, message) Broker->>Subscriber: PUBLISH (topic, message) Note over Subscriber,Broker: Subscriber receives message Subscriber->>Broker: PUBACK Broker->>Client: PUBACK

Customizing and Extending the Broker

Both Comqtt and Mochi MQTT are designed to be highly customizable and extendable.

Using Configuration Files

You can customize the broker’s behavior using configuration files. For example, with Comqtt, you can specify multiple authentication methods and bridge configurations in the single.yml file[1].

Hook-Based Interfacing System

Mochi MQTT provides a full-featured and flexible hook-based interfacing system, allowing you to develop plugins easily. Here’s an example of how you might add a custom hook:

import (
    "github.com/mochi-co/mqtt/server"
    "github.com/mochi-co/mqtt/server/hooks"
)

func main() {
    // Create the new MQTT Server.
    server := server.NewServer(nil)

    // Add a custom hook.
    server.AddHook(hooks.OnConnect, func(client *server.Client, packet *server.ConnectPacket) {
        // Custom logic on client connect.
        log.Println("Client connected:", client.ID)
    })

    // Start the broker.
    err := server.Serve()
    if err != nil {
        log.Fatal(err)
    }
}

Conclusion

Developing a high-performance MQTT broker in Go is a rewarding task that leverages the strengths of both the MQTT protocol and the Go language. Whether you choose Comqtt or Mochi MQTT, you’ll have a robust and customizable solution for your IoT and smart home projects.

Remember, the key to a successful MQTT broker is not just about the code; it’s about understanding the protocol, the architecture, and how to customize it to fit your specific needs. Happy coding