automatically attempt to reconnect to the MQTT if we fail to send a message

autoplant_pio/src/autoplant.cpp

@@ -66,6 +66,10 @@ PubSubClient mqtt;
 
 Adafruit_BME280 bme;	// I2C
 
+/**
+ * Connect to the WiFi.
+ * @return	void
+ */
 void connect_wifi() {
 #ifndef WIFI_ENTERPRISE_ENABLED
 	Serial.print("personal");
@@ -94,7 +98,64 @@ void connect_wifi() {
 #endif
 }
 
+/**
+ * (Re)connect to the MQTT server.
+ * @return	void
+ */
+void connect_mqtt() {
+	int delay = 1000;
+	while(true) {
+		Serial.print("MQTT: ");
+		mqtt = PubSubClient();
+#ifdef MQTT_NO_TLS
+		Serial.print("notls");
+#else
+		Serial.print("tls");
+		transport.setInsecure(); Serial.print(".");
+#endif
+		// mqtt.setBufferSize(1000);
+		mqtt.setClient(transport); Serial.print(".");
+		mqtt.setServer(MQTT_SERVER, MQTT_PORT); Serial.print(".");
+		// Serial.print(MQTT_SERVER);
+		// Serial.print(":");
+		// Serial.print(MQTT_PORT);
+		// Serial.print(".");
+		if(mqtt.connect(
+			("autoplant_" + String(random(0, 999999))).c_str(),
+			MQTT_USERNAME, MQTT_PASSWORD)
+		) {
+			break;
+		}
+		
+		/* Ref https://pubsubclient.knolleary.net/api#state
+		-4 : MQTT_CONNECTION_TIMEOUT - the server didn't respond within the keepalive time
+		-3 : MQTT_CONNECTION_LOST - the network connection was broken
+		-2 : MQTT_CONNECT_FAILED - the network connection failed
+		-1 : MQTT_DISCONNECTED - the client is disconnected cleanly
+		0 : MQTT_CONNECTED - the client is connected
+		1 : MQTT_CONNECT_BAD_PROTOCOL - the server doesn't support the requested version of MQTT
+		2 : MQTT_CONNECT_BAD_CLIENT_ID - the server rejected the client identifier
+		3 : MQTT_CONNECT_UNAVAILABLE - the server was unable to accept the connection
+		4 : MQTT_CONNECT_BAD_CREDENTIALS - the username/password were rejected
+		5 : MQTT_CONNECT_UNAUTHORIZED - the client was not authorized to connect
+		*/
+		int error_code = mqtt.state();
+		Serial.println("failed, error code "+String(error_code));
+		
+		delay(delay);
+		delay += 1000;
+		if(delay > 60 * 1000) delay = 60 * 1000;
+	}
+	
+	Serial.println("ok");
+}
 
+/**
+ * Read an analogue value from a sensor.
+ *
+ * @param	int		channel		The channel on the analogue shift register to read from.
+ * @return	float	The analogue voltage read.
+ */
 float read_analog(int channel) {
 	
 	const char* bin = std::bitset<8>(channel).to_string().c_str();
@@ -113,6 +174,15 @@ float read_analog(int channel) {
 	return parsedValue;
 }
 
+/**
+ * Send an MQTT message.
+ * Does *not* attempt to reconnect if it fails.
+ * 
+ * @param	String	id		The 'hostname' of the sensor machine.
+ * @param	String	sensor	The name of the sensor.
+ * @param	float	value	The sensor value to send.
+ * @return  bool	Whether the MQTT messaage was sent successfully or not.
+ */
 bool send_mqtt(String id, String sensor, float value) {
 	// StaticJsonDocument<96> data;
 	// 
@@ -131,6 +201,26 @@ bool send_mqtt(String id, String sensor, float value) {
 	return result;
 }
 
+/**
+ * Send an MQTT message.
+ * Automatically attempts to reconnect if the connection fails for some reason.
+ * 
+ * @param	String	id		The 'hostname' of the sensor machine.
+ * @param	String	sensor	The name of the sensor.
+ * @param	float	value	The sensor value to send.
+ * @return  bool	Whether the MQTT messaage was sent successfully or not.
+ */
+bool do_send_mqtt(String id, String sensor, float value) {
+	bool result = send_mqtt(id, sensor, value);
+	if(!result) {
+		Serial.print("[mqtt] connection lost, error ");
+		Serial.println(value);
+		connect_mqtt();
+	}
+	result = send_mqtt(id, sensor, value);
+	return result;
+}
+
 void setup() {
 	Serial.begin(9600);
 	delay(1000);
@@ -167,42 +257,7 @@ void setup() {
 		Serial.println(WiFi.status());
 	}
 	
-	Serial.print("MQTT: ");
+	connect_mqtt();
-#ifdef MQTT_NO_TLS
-	Serial.print("notls");
-#else
-	Serial.print("tls");
-	transport.setInsecure(); Serial.print(".");
-#endif
-	// mqtt.setBufferSize(1000);
-	mqtt.setClient(transport); Serial.print(".");
-	mqtt.setServer(MQTT_SERVER, MQTT_PORT); Serial.print(".");
-	// Serial.print(MQTT_SERVER);
-	// Serial.print(":");
-	// Serial.print(MQTT_PORT);
-	// Serial.print(".");
-	
-	if(!mqtt.connect(
-		("autoplant_" + String(random(0, 999999))).c_str(),
-		MQTT_USERNAME, MQTT_PASSWORD)
-	) {
-		/* Ref https://pubsubclient.knolleary.net/api#state
-		-4 : MQTT_CONNECTION_TIMEOUT - the server didn't respond within the keepalive time
-		-3 : MQTT_CONNECTION_LOST - the network connection was broken
-		-2 : MQTT_CONNECT_FAILED - the network connection failed
-		-1 : MQTT_DISCONNECTED - the client is disconnected cleanly
-		0 : MQTT_CONNECTED - the client is connected
-		1 : MQTT_CONNECT_BAD_PROTOCOL - the server doesn't support the requested version of MQTT
-		2 : MQTT_CONNECT_BAD_CLIENT_ID - the server rejected the client identifier
-		3 : MQTT_CONNECT_UNAVAILABLE - the server was unable to accept the connection
-		4 : MQTT_CONNECT_BAD_CREDENTIALS - the username/password were rejected
-		5 : MQTT_CONNECT_UNAUTHORIZED - the client was not authorized to connect
-		*/
-		int error_code = mqtt.state();
-		Serial.println("failed, error code "+String(error_code));
-		while(true) delay(10000);
-	}
-	Serial.println("ok");
 	
 	Serial.print("BME280: ");
 	
@@ -225,38 +280,38 @@ void loop() {
 	
 	// StaticJsonDocument<96> data;
 	
-	if(!send_mqtt(
+	if(!do_send_mqtt(
 		"autoplant-a",
 		"soil",
 		soil_a
 	)) Serial.println("[mqtt] Failed to send message");
-	if(!send_mqtt(
+	if(!do_send_mqtt(
 		"autoplant-a",
 		"water-level",
 		water_level_a
 	)) Serial.println("[mqtt] Failed to send message");
-	if(!send_mqtt(
+	if(!do_send_mqtt(
 		"autoplant-b",
 		"soil",
 		soil_b
 	)) Serial.println("[mqtt] Failed to send message");
-	if(!send_mqtt(
+	if(!do_send_mqtt(
 		"autoplant-b",
 		"water-level",
 		water_level_b
 	)) Serial.println("[mqtt] Failed to send message");
 	
-	if(!send_mqtt(
+	if(!do_send_mqtt(
 		"autoplant-a",
 		"temperature",
 		temp
 	)) Serial.println("[mqtt] Failed to send message");
-	if(!send_mqtt(
+	if(!do_send_mqtt(
 		"autoplant-a",
 		"humidity",
 		humidity
 	)) Serial.println("[mqtt] Failed to send message");
-	if(!send_mqtt(
+	if(!do_send_mqtt(
 		"autoplant-a",
 		"pressure",
 		pressure