[Issue #8] - adding MQTT reconnect if the connection drops

main.go

@@ -36,8 +36,8 @@ func (m *SimpleMQTT) Connect(clientID, username, password string) error {
 		flags |= 0x40
 	}
 
-	// Variable header: MQTT (proto name), Level 4 (MQTT 3.1.1), flags, KeepAlive 60s
-	varHeader := []byte{0x00, 0x04, 'M', 'Q', 'T', 'T', 0x04, flags, 0x00, 0x3C}
+	// Variable header: MQTT (proto name), Level 4 (MQTT 3.1.1), flags, KeepAlive 0s (disabled)
+	varHeader := []byte{0x00, 0x04, 'M', 'Q', 'T', 'T', 0x04, flags, 0x00, 0x00}
 
 	payload := encodeString(clientID)
 	if username != "" {
@@ -145,7 +145,7 @@ func registerHADiscovery(mqtt *SimpleMQTT, sensor ClimateSensor) error {
 }
 
 // -------------------------------------------------------------
-// Panic Handler & Entry Point
+// Panic Handler & Helper Functions
 // -------------------------------------------------------------
 func panicErr(msg string, err error) {
 	if err != nil {
@@ -156,6 +156,22 @@ func panicErr(msg string, err error) {
 	}
 }
 
+func connectMQTT(netStack *NetworkStack, port uint16) (*SimpleMQTT, error) {
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+
+	conn, err := netStack.DialTCP(ctx, MQTTHost, port)
+	if err != nil {
+		return nil, err
+	}
+
+	mqtt := NewSimpleMQTT(conn)
+	if err := mqtt.Connect(ClientID, MQTTUser, MQTTPass); err != nil {
+		return nil, err
+	}
+	return mqtt, nil
+}
+
 func main() {
 	time.Sleep(2 * time.Second)
 
@@ -205,17 +221,10 @@ func main() {
 	}
 
 	portNum, _ := strconv.Atoi(MQTTPort)
-	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
-	defer cancel()
 
-	conn, err := netStack.DialTCP(ctx, MQTTHost, uint16(portNum))
-	if err != nil {
-		panicErr("TCP dial", err)
-	}
-
-	mqtt := NewSimpleMQTT(conn)
 	println("Connecting MQTT session...")
-	if err := mqtt.Connect(ClientID, MQTTUser, MQTTPass); err != nil {
+	mqtt, err := connectMQTT(netStack, uint16(portNum))
+	if err != nil {
 		panicErr("MQTT connect", err)
 	}
 	println("MQTT connected.")
@@ -237,7 +246,16 @@ func main() {
 			}
 
 			if err := mqtt.Publish(StateTopic, []byte(stateJSON), false); err != nil {
-				println("MQTT publish error:", err.Error())
+				println("MQTT publish error:", err.Error(), "- attempting reconnect...")
+				newMqtt, recErr := connectMQTT(netStack, uint16(portNum))
+				if recErr != nil {
+					println("MQTT reconnect failed:", recErr.Error())
+				} else {
+					println("MQTT reconnected successfully.")
+					mqtt = newMqtt
+					_ = registerHADiscovery(mqtt, sensor)
+					_ = mqtt.Publish(StateTopic, []byte(stateJSON), false)
+				}
 			} else {
 				println(fmt.Sprintf("[%s] Published: %s", NodeName, stateJSON))
 			}