Added retain flag for publishing

Adafruit_MQTT.cpp

@@ -337,15 +337,15 @@ bool Adafruit_MQTT::disconnect() {
   return disconnectServer();
 }
 
-bool Adafruit_MQTT::publish(const char *topic, const char *data, uint8_t qos) {
+bool Adafruit_MQTT::publish(const char *topic, const char *data, uint8_t qos, uint8_t retain) {
-  return publish(topic, (uint8_t *)(data), strlen(data), qos);
+  return publish(topic, (uint8_t *)(data), strlen(data), qos, retain);
 }
 
 bool Adafruit_MQTT::publish(const char *topic, uint8_t *data, uint16_t bLen,
-                            uint8_t qos) {
+                            uint8_t qos, uint8_t retain) {
   // Construct and send publish packet.
   uint16_t len =
-      publishPacket(buffer, topic, data, bLen, qos, (uint16_t)sizeof(buffer));
+      publishPacket(buffer, topic, data, bLen, qos, (uint16_t)sizeof(buffer), retain);
   if (!sendPacket(buffer, len))
     return false;
 
@@ -743,7 +743,7 @@ uint8_t Adafruit_MQTT::connectPacket(uint8_t *packet) {
 // http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc398718040
 uint16_t Adafruit_MQTT::publishPacket(uint8_t *packet, const char *topic,
                                       uint8_t *data, uint16_t bLen, uint8_t qos,
-                                      uint16_t maxPacketLen) {
+                                      uint16_t maxPacketLen, uint8_t retain) {
   uint8_t *p = packet;
   uint16_t len = 0;
 
@@ -773,7 +773,7 @@ uint16_t Adafruit_MQTT::publishPacket(uint8_t *packet, const char *topic,
   len += bLen; // remaining len excludes header byte & length field
 
   // Now you can start generating the packet!
-  p[0] = MQTT_CTRL_PUBLISH << 4 | qos << 1;
+  p[0] = MQTT_CTRL_PUBLISH << 4 | qos << 1 | (retain ? 1 : 0);
   p++;
 
   // fill in packet[1] last
@@ -893,38 +893,39 @@ uint8_t Adafruit_MQTT::disconnectPacket(uint8_t *packet) {
 // Adafruit_MQTT_Publish Definition ////////////////////////////////////////////
 
 Adafruit_MQTT_Publish::Adafruit_MQTT_Publish(Adafruit_MQTT *mqttserver,
-                                             const char *feed, uint8_t q) {
+                                             const char *feed, uint8_t q, uint8_t r) {
   mqtt = mqttserver;
   topic = feed;
   qos = q;
+  retain = r;
 }
 bool Adafruit_MQTT_Publish::publish(int32_t i) {
   char payload[12];
   ltoa(i, payload, 10);
-  return mqtt->publish(topic, payload, qos);
+  return mqtt->publish(topic, payload, qos, retain);
 }
 
 bool Adafruit_MQTT_Publish::publish(uint32_t i) {
   char payload[11];
   ultoa(i, payload, 10);
-  return mqtt->publish(topic, payload, qos);
+  return mqtt->publish(topic, payload, qos, retain);
 }
 
 bool Adafruit_MQTT_Publish::publish(double f, uint8_t precision) {
   char payload[41]; // Need to technically hold float max, 39 digits and minus
                     // sign.
   dtostrf(f, 0, precision, payload);
-  return mqtt->publish(topic, payload, qos);
+  return mqtt->publish(topic, payload, qos, retain);
 }
 
 bool Adafruit_MQTT_Publish::publish(const char *payload) {
-  return mqtt->publish(topic, payload, qos);
+  return mqtt->publish(topic, payload, qos, retain);
 }
 
 // publish buffer of arbitrary length
 bool Adafruit_MQTT_Publish::publish(uint8_t *payload, uint16_t bLen) {
 
-  return mqtt->publish(topic, payload, bLen, qos);
+  return mqtt->publish(topic, payload, bLen, qos, retain);
 }
 
 // Adafruit_MQTT_Subscribe Definition //////////////////////////////////////////

Adafruit_MQTT.h

@@ -189,9 +189,9 @@ public:
 
   // Publish a message to a topic using the specified QoS level.  Returns true
   // if the message was published, false otherwise.
-  bool publish(const char *topic, const char *payload, uint8_t qos = 0);
+  bool publish(const char *topic, const char *payload, uint8_t qos = 0, uint8_t retain = 0);
   bool publish(const char *topic, uint8_t *payload, uint16_t bLen,
-               uint8_t qos = 0);
+               uint8_t qos = 0, uint8_t retain = 0);
 
   // Add a subscription to receive messages for a topic.  Returns true if the
   // subscription could be added or was already present, false otherwise.
@@ -266,7 +266,7 @@ private:
   uint8_t connectPacket(uint8_t *packet);
   uint8_t disconnectPacket(uint8_t *packet);
   uint16_t publishPacket(uint8_t *packet, const char *topic, uint8_t *payload,
-                         uint16_t bLen, uint8_t qos, uint16_t maxPacketLen = 0);
+                         uint16_t bLen, uint8_t qos, uint16_t maxPacketLen = 0, uint8_t retain = 0);
   uint8_t subscribePacket(uint8_t *packet, const char *topic, uint8_t qos);
   uint8_t unsubscribePacket(uint8_t *packet, const char *topic);
   uint8_t pingPacket(uint8_t *packet);
@@ -276,7 +276,7 @@ private:
 class Adafruit_MQTT_Publish {
 public:
   Adafruit_MQTT_Publish(Adafruit_MQTT *mqttserver, const char *feed,
-                        uint8_t qos = 0);
+                        uint8_t qos = 0, uint8_t retain = 0);
 
   bool publish(const char *s);
   bool publish(
@@ -292,6 +292,7 @@ private:
   Adafruit_MQTT *mqtt;
   const char *topic;
   uint8_t qos;
+  uint8_t retain;
 };
 
 class Adafruit_MQTT_Subscribe {