golang implements mqtt

In recent years, with the development of IoT technology, the MQTT protocol has gradually occupied an important position in the field of IoT communication. MQTT (Message Queuing Telemetry Transport) is a lightweight communication protocol based on the publish/subscribe (pub/sub) model. The MQTT protocol is simple, efficient, reliable, and flexible, and can be applied to various devices such as mobile phones, embedded systems, and PCs, especially in the field of the Internet of Things. This article will introduce how to implement the MQTT protocol using Go language.

1. Introduction to MQTT protocol

The MQTT protocol is a protocol designed for communication needs in low-bandwidth, high-latency, and unstable network environments. MQTT introduces the idea of ​​​​a publish/subscribe model, that is, the message delivery between the message publisher (Publisher) and the message subscriber (Subscriber) is not directly connected, but is implemented through an intermediate proxy server (Broker).

The message format of the MQTT protocol is as follows:

——— ——— ——— ——— ——— ——— ——— ——— ——— ——— — —— ——— ——— ———
|Fixed header|Variable header|Message body|
——— ——— ——— ——— ——— ——— —— — ——— ——— ——— ——— ——— ——— ———

Fixed header: Contains message type, QoS and other information.
Variable header: Contains some fixed information of the secondary protocol, such as client ID, topic name, etc.
Message body: the specific content of publishing or subscribing.

2. Go language implements MQTT

Go language is an emerging programming language known for its excellent concurrency and efficient performance. It has also recently become a popular language in the field of Internet of Things. One of the popular languages. Go language provides some excellent network programming libraries, such as TCP, UDP, HTTP, etc. You can use the excellent features of Go language and these libraries to easily implement the MQTT protocol.

2.1 Install mqtt library

Go language provides multiple mqtt libraries, such as Paho MQTT, Eclipse Paho, etc. This article will use the Eclipse Paho library, which is installed through the following command:

go get github.com/eclipse/paho.mqtt.golang

2.2 Connecting to the MQTT server

Before using the Eclipse Paho library, you need to connect to the MQTT proxy server. When connecting, you need to provide MQTT proxy server address, client ID, user name, password and other information.

The MQTT library provides the ClientOptions type, and the connection options are set through the SetXXX method of this type, such as:

opts := mqtt.NewClientOptions().AddBroker("tcp://localhost:1883").SetClientID("go-mqtt")
opts.SetUsername("user")
opts.SetPassword("password")
client := mqtt.NewClient(opts)

In the above code, the AddBroker method sets the MQTT proxy server address, and the SetClientID method sets the client ID. , SetUsername and SetPassword methods set connection authentication information.

2.3 Publishing Messages

In the MQTT protocol, the publishing end of the message is the client that publishes the message. When publishing the message, the subject and content of the message need to be provided. The Eclipse Paho library provides the Publish method for sending messages. As shown below:

token := client.Publish("topic", 0, false, "hello world")
token.Wait()

In the above code, the first parameter of the client.Publish method is the topic name, the second parameter is the QoS level, and the third parameter is the Retain flag (true means the server will save the last A message of the corresponding topic and sends it when the topic is newly subscribed), the fourth parameter is the message body.

2.4 Subscribing to messages

In the MQTT protocol, the subscriber of the message needs to provide the topic that needs to be subscribed, and needs to provide a callback function to process the message when it arrives. The Eclipse Paho library provides the Subscribe method for subscribing to messages. As shown below:

token := client.Subscribe("topic", 0, func(client mqtt.Client, msg mqtt.Message) {
    fmt.Printf("Received message: %s from topic: %s
", msg.Payload(), msg.Topic())
})
token.Wait()

In the above code, the first parameter of the client.Subscribe method is the topic name, the second parameter is the QoS level, and the third parameter is the callback function, which will be called when the message arrives. time execution.

3. Summary

Through the above sample code, we can see that it is very simple to implement the MQTT protocol using the Go language and the Eclipse Paho library. Go language has good concurrency performance and network programming library, and can easily implement various network communication protocols. As a lightweight communication protocol, the MQTT protocol has a wide range of applications in the field of the Internet of Things. Implementing the MQTT protocol through the Go language can provide a more efficient, secure and reliable communication method for Internet of Things applications. I believe that in the development of the Internet of Things In the future, MQTT protocol and Go language will be more and more widely used in the field of Internet of Things.

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