This article describes how to use the Paho Message Queuing Telemetry Transport (MQTT)
library for Go to connect to IoT Platform and exchange messages with IoT Platform.
Prepare the development environment
Install the Go language package.
Download the Paho MQTT library for Go
For more information about the Paho project and supported development languages, visit
Eclipse Paho Downloads.
Run the following commands to download the Paho MQTT library for Go and the dependencies:
go get github.com/eclipse/paho.mqtt.golang
go get github.com/gorilla/websocket
go get golang.org/x/net/proxy
Connect to IoT Platform
- Click MqttSign.go to obtain the source code provided by Alibaba Cloud to calculate the MQTT connection
parameters.
The MqttSign.go file defines the function that calculates the MQTT connection parameters used by
a device to connect to IoT Platform. Your device program for connecting to IoT Platform
must call this function.
- Prototype
type AuthInfo struct {
password, username, mqttClientId string;
}
func calculate_sign(clientId, productKey, deviceName, deviceSecret, timeStamp string) AuthInfo;
- Description
Calculates the MQTT connection parameters username, password, and mqttClientId.
- Input parameters
Parameter |
Type |
Description |
productKey |
String |
The ProductKey of the product to which the device belongs. It can be used to identify
the device in IoT Platform.
|
deviceName |
String |
The DeviceName of the device. It can be used to identify the device in IoT Platform. |
deviceSecret |
String |
The DeviceSecret of the device. It can be used to identify the device in IoT Platform. |
clientId |
String |
The ID of the device. It can be set to a string of no more than 64 characters. We
recommend that you use the MAC address or serial number (SN) of the device as the
ID.
|
timeStamp |
String |
The timestamp of the current time in milliseconds. |
- Output parameters
The return value of this function is an AuthInfo
structure that contains the parameters described in the following table.
Parameter |
Type |
Description |
username |
String |
The username that is used to establish the MQTT connection. |
password |
String |
The password that is used to establish the MQTT connection. |
mqttClientId |
String |
The ID of the MQTT client. |
- Add a program file that can connect a device to IoT Platform.
You must write a program to call the MqttSign.go file to calculate the parameters that are used to establish an MQTT connection to
IoT Platform.
This section provides the development instructions and sample code.
- Set the device information.
// set the device info, include product key, device name, and device secret
var productKey string = "a1Zd7n5***"
var deviceName string = "testdevice"
var deviceSecret string = "UrwclDV33NaFSmk0JaBxNTqgSrJW****"
// set timestamp, clientid, subscribe topic and publish topic
var timeStamp string = "1528018257135"
var clientId string = "192.168.****"
var subTopic string = "/" + productKey + "/" + deviceName + "/user/get";
var pubTopic string = "/" + productKey + "/" + deviceName + "/user/update";
- Set the MQTT connection information.
Call the calculate_sign() function defined in MqttSign.go file. This function calculates the username, password, and mqttClientId parameters based on the input parameters clientId, productKey, deviceName, deviceSecret, and timeStamp. Add the calculation result to the opts structure.
// set the login broker url
var raw_broker bytes.Buffer
raw_broker.WriteString("tls://")
raw_broker.WriteString(productKey)
raw_broker.WriteString(".iot-as-mqtt.cn-shanghai.aliyuncs.com:1883")
opts := MQTT.NewClientOptions().AddBroker(raw_broker.String());
// calculate the login auth info, and set it into the connection options
auth := calculate_sign(clientId, productKey, deviceName, deviceSecret, timeStamp)
opts.SetClientID(auth.mqttClientId)
opts.SetUsername(auth.username)
opts.SetPassword(auth.password)
opts.SetKeepAlive(60 * 2 * time.Second)
opts.SetDefaultPublishHandler(f)
Note Replace cn-shanghai in the code with the ID of the region where your device resides.
For more information about region IDs, see
Regions and zones.
- Call the MQTT Connect() function to connect to IoT Platform.
// create and start a client using the above ClientOptions
c := MQTT.NewClient(opts)
if token := c.Connect(); token.Wait() && token.Error() ! = nil {
panic(token.Error())
}
fmt.Print("Connect aliyun IoT Cloud Sucess\n");
- Call the Publish() function to publish messages. You must specify the topic to which messages are published
and the payload of the published messages.
// publish 5 messages to pubTopic("/a1Zd7n5****/deng/user/update")
for i := 0; i < 5; i++ {
fmt.Println("publish msg:", i)
text := fmt.Sprintf("ABC #%d", i)
token := c.Publish(pubTopic, 0, false, text)
fmt.Println("publish msg: ", text)
token.Wait()
time.Sleep(2 * time.Second)
}
For more information about communication topics, see What is a topic?
- Call the Subscribe() function to subscribe to the topic for receiving messages from IoT Platform.
// subscribe to subTopic("/a1Zd7n5***/deng/user/get") and request messages to be delivered
if token := c.Subscribe(subTopic, 0, nil); token.Wait() && token.Error() ! = nil {
fmt.Println(token.Error())
os.Exit(1)
}
fmt.Print("Subscribe topic " + subTopic + " success\n");
For more information about the communication methods of devices, servers, and IoT
Platform, see Overview.
- Compile the project.
Demo
The demo code demonstrates how to connect a device to IoT Platform.
- Download the demo package and decompress it.
The following table describes the files that are contained in the
aiot-go-demo package.
File |
Description |
MqttSign.go |
This file contains the code that is used to calculate the parameters for establishing
an MQTT connection to IoT Platform. When you run the iot.go file, the calculate_sign() function is called to calculate the connection parameters username, password, and mqttClientId.
|
iot.go |
This file contains the logic code that is used to establish a connection and exchange
messages between the device and IoT Platform.
|
x509 |
The root certificate of IoT Platform. This certificate is required by the device to
connect to IoT Platform.
|
- In the iot.go file, replace the device information with your device information.
You can use tools such as Linux vi to modify the iot.go file.
- Run the following command in the command line to run the iot.go file:
go run iot.go MqttSign.go
After the file is run, you can view the local logs about the connection to IoT Platform.
clientId192.168.****deviceNametestdeviceproductKeya1Zd7n5****timestamp1528018257135
1b865320fc183cc747041c9faffc9055fc45****
Connect aliyun IoT Cloud Sucess
Subscribe topic /a1Zd7n5****/testdevice/user/get success
publish msg: 0
publish msg: ABC #0
publish msg: 1
publish msg: ABC #1
publish msg: 2
publish msg: ABC #2
publish msg: 3
publish msg: ABC #3
publish msg: 4
publish msg: ABC #4
publish msg: 5
publish msg: ABC #5
Log on to the IoT Platform console.View device status and logs.
Error codes
If a device fails to establish an MQTT connection to IoT Platform, you can troubleshoot
the issue based on the error code. For more information about the error codes that
may be returned by IoT Platform, see Troubleshooting.