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package main
import (
"fmt"
"log"
"time"
mqtt "github.com/eclipse/paho.mqtt.golang"
)
const (
QOS = byte(1)
RETAINED = true
MQTT_CONNECT_TIMEOUT = 1 * time.Second
MQTT_DISCONNECT_TIMEOUT_US = 500
MQTT_KEEPALIVE_PERIOD = 2 * time.Second
)
var (
mqttServerHealthTopic string
)
type MQTTMessage struct {
Topic string
Payload []byte
}
func MQTTRun(config MQTTConfig, tx chan MQTTMessage) {
mqttServerHealthTopic = fmt.Sprintf("%s/server/health", config.TopicPrefix)
opts := mqtt.NewClientOptions()
opts.AddBroker(config.Broker)
opts.SetClientID(config.ClientID)
opts.SetCleanSession(true)
opts.SetOnConnectHandler(MQTTOnConnectHandler)
opts.SetConnectionLostHandler(MQTTConnectionLostHandler)
opts.SetAutoReconnect(true)
opts.SetConnectRetry(true)
opts.SetConnectTimeout(MQTT_CONNECT_TIMEOUT)
opts.SetKeepAlive(MQTT_KEEPALIVE_PERIOD)
opts.SetWill(mqttServerHealthTopic, `bad`, QOS, true)
client := mqtt.NewClient(opts)
token := client.Connect()
success := token.WaitTimeout(MQTT_CONNECT_TIMEOUT)
if !success {
log.Fatal("Initial connection to MQTT broker failed.")
}
defer client.Disconnect(MQTT_DISCONNECT_TIMEOUT_US)
for message := range tx {
topic := fmt.Sprintf("%s/%s", config.TopicPrefix, message.Topic)
client.Publish(topic, QOS, RETAINED, message.Payload)
}
}
func MQTTOnConnectHandler(c mqtt.Client) {
log.Printf("Connected to MQTT broker.")
c.Publish(mqttServerHealthTopic, QOS, true, []byte(`good`))
}
func MQTTConnectionLostHandler(c mqtt.Client, err error) {
log.Printf("Connection to MQTT broker lost: %v", err)
}
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