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package main
import (
"fmt"
"log"
"time"
"strings"
mqtt "github.com/eclipse/paho.mqtt.golang"
)
const (
QoS0 = byte(0)
QoS1 = byte(1)
QoS2 = byte(2)
RETAINED = true
MQTT_CONNECT_TIMEOUT = 1 * time.Second
MQTT_SUBSCRIBE_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
Retain bool
}
type Route struct {
Topic string
QoS byte
Destination chan MQTTMessage
}
func NewRoute(topic string, qos byte) Route {
return Route{topic, qos, make(chan MQTTMessage)}
}
func (m MQTTMessage) String() string {
return fmt.Sprintf("topic='%s' message='%s'", m.Topic, string(m.Payload))
}
func MQTTRun(config MQTTConfig, tx chan MQTTMessage, routes ...Route) {
mqttServerHealthTopic = fmt.Sprintf("%s/server/health", config.TopicPrefix)
mqttServerVersionTopic := fmt.Sprintf("%s/server/version", config.TopicPrefix)
opts := mqtt.NewClientOptions()
opts.AddBroker(config.Broker)
opts.SetClientID(config.ClientID)
opts.SetCleanSession(true)
opts.SetOnConnectHandler(func(c mqtt.Client) {
log.Printf("Connected to MQTT broker.")
c.Publish(mqttServerHealthTopic, QoS1, true, []byte(`good`))
c.Publish(mqttServerVersionTopic, QoS1, true, []byte(Version()))
for _, route := range routes {
topic := config.TopicPrefix + "/" + route.Topic
token := c.Subscribe(topic, route.QoS, func(c mqtt.Client, msg mqtt.Message) {
message := MQTTMessage{
Topic: strings.TrimPrefix(msg.Topic(), config.TopicPrefix + "/"),
Payload: msg.Payload(),
Retain: msg.Retained(),
}
route.Destination <- message
})
success := token.WaitTimeout(MQTT_SUBSCRIBE_TIMEOUT)
if !success {
log.Fatalf("Topic subscription failed for topic '%s'", topic)
}
}
})
opts.SetConnectionLostHandler(MQTTConnectionLostHandler)
opts.SetAutoReconnect(true)
opts.SetConnectRetry(true)
opts.SetConnectTimeout(MQTT_CONNECT_TIMEOUT)
opts.SetKeepAlive(MQTT_KEEPALIVE_PERIOD)
opts.SetWill(mqttServerHealthTopic, `bad`, QoS1, 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, QoS1, message.Retain, message.Payload)
}
}
func MQTTConnectionLostHandler(c mqtt.Client, err error) {
log.Printf("Connection to MQTT broker lost: %v", err)
}
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