Add connected() function to MQTT class. Update examples with robust reconnect logic.

Adafruit_MQTT.h

@@ -111,6 +111,9 @@ class Adafruit_MQTT {
   // otherwise.
   virtual bool disconnect() = 0;  // Subclasses need to fill this in!
 
+  // Return true if connected to the MQTT server, otherwise false.
+  virtual bool connected() = 0;  // Subclasses need to fill this in!
+
   // 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, char *payload, uint8_t qos);

Adafruit_MQTT_CC3000.h

@@ -82,7 +82,16 @@ class Adafruit_MQTT_CC3000 : public Adafruit_MQTT {
   }
 
   bool disconnect() {
-    return (mqttclient.close() == 0); 
+    if (connected()) {
+      return (mqttclient.close() == 0);
+    }
+    else {
+      return true;
+    }
+  }
+
+  bool connected() {
+    return mqttclient.connected();
   }
 
   uint16_t readPacket(uint8_t *buffer, uint8_t maxlen, int16_t timeout,

Adafruit_MQTT_Client.cpp

@@ -34,11 +34,19 @@ bool Adafruit_MQTT_Client::connectServer() {
 }
 
 bool Adafruit_MQTT_Client::disconnect() {
-  // Stop connection and return success (stop has no indication of failure).
+  // Stop connection if connected and return success (stop has no indication of
-  client->stop();
+  // failure).
+  if (client->connected()) {
+    client->stop();
+  }
   return true;
 }
 
+bool Adafruit_MQTT_Client::connected() {
+  // Return true if connected, false if not connected.
+  return client->connected();
+}
+
 uint16_t Adafruit_MQTT_Client::readPacket(uint8_t *buffer, uint8_t maxlen,
                                           int16_t timeout,
                                           bool checkForValidPubPacket) {

Adafruit_MQTT_Client.h

@@ -44,6 +44,7 @@ class Adafruit_MQTT_Client : public Adafruit_MQTT {
 
   bool connectServer();
   bool disconnect();
+  bool connected();
   uint16_t readPacket(uint8_t *buffer, uint8_t maxlen, int16_t timeout,
                       bool checkForValidPubPacket = false);
   bool sendPacket(uint8_t *buffer, uint8_t len);

Adafruit_MQTT_FONA.h

@@ -55,6 +55,11 @@ class Adafruit_MQTT_FONA : public Adafruit_MQTT {
     return fona->TCPclose();
   }
 
+  bool connected() {
+    // Return true if connected, false if not connected.
+    return fona->TCPconnected();
+  }
+
   uint16_t readPacket(uint8_t *buffer, uint8_t maxlen, int16_t timeout,
                       bool checkForValidPubPacket = false) {
     uint8_t *buffp = buffer;

examples/mqtt_cc3k/mqtt_cc3k.ino

@@ -93,31 +93,6 @@ void setup() {
     Serial.println(F("Retrying WiFi"));
     while(1);
   }
-
-  Serial.println(F("Connected to WiFi!"));
-  //////////////////////////////
-  Serial.println(F("Connecting to MQTT..."));
-  int8_t ret;
-  while ((ret = mqtt.connect()) != 0) {
-       switch (ret) {
-          case 1: Serial.println(F("Wrong protocol")); break;
-          case 2: Serial.println(F("ID rejected")); break;
-          case 3: Serial.println(F("Server unavail")); break;
-          case 4: Serial.println(F("Bad user/pass")); break;
-          case 5: Serial.println(F("Not authed")); break;
-          case 6: Serial.println(F("Failed to subscribe")); break;
-          default: {
-            Serial.println(F("Connection failed")); 
-            CC3000connect(WLAN_SSID, WLAN_PASS, WLAN_SECURITY);  // y0w, lets connect to wifi again
-            return;           // restart the loop
-          }
-       }
-       Serial.println(F("Retrying MQTT connection"));
-       delay(5000); 
-  }
-  //////////////////////////////
-
-  Serial.println(F("MQTT Connected!"));  
 }
 
 uint32_t x=0;
@@ -126,6 +101,11 @@ void loop() {
   // Make sure to reset watchdog every loop iteration!
   Watchdog.reset();
 
+  // Ensure the connection to the MQTT server is alive (this will make the first
+  // connection and automatically reconnect when disconnected).  See the MQTT_connect
+  // function definition further below.
+  MQTT_connect();
+ 
   // Try to ping the MQTT server
   /*
   if (! mqtt.ping(3) ) {
@@ -155,3 +135,35 @@ void loop() {
     Serial.println(F("OK!"));
   }
 }
+
+// Function to connect and reconnect as necessary to the MQTT server.
+// Should be called in the loop function and it will take care if connecting.
+void MQTT_connect() {
+  int8_t ret;
+
+  // Stop if already connected.
+  if (mqtt.connected()) {
+    return;
+  }
+
+  Serial.print("Connecting to MQTT... ");
+
+  while ((ret = mqtt.connect()) != 0) { // connect will return 0 for connected
+       switch (ret) {
+          case 1: Serial.println("Wrong protocol"); break;
+          case 2: Serial.println("ID rejected"); break;
+          case 3: Serial.println("Server unavailable"); break;
+          case 4: Serial.println("Bad user/password"); break;
+          case 5: Serial.println("Not authenticated"); break;
+          case 6: Serial.println("Failed to subscribe"); break;
+          default:
+            Serial.println(F("Connection failed"));
+            CC3000connect(WLAN_SSID, WLAN_PASS, WLAN_SECURITY);  // y0w, lets connect to wifi again
+            break;
+       }
+       Serial.println("Retrying MQTT connection in 5 seconds...");
+       mqtt.disconnect();
+       delay(5000);  // wait 5 seconds
+  }
+  Serial.println("MQTT Connected!");
+}

examples/mqtt_esp8266/mqtt_esp8266.ino

@@ -81,30 +81,16 @@ void setup() {
 
   // Setup MQTT subscription for onoff feed.
   mqtt.subscribe(&onoffbutton);
-
-  // Connect to MQTT server.
-  Serial.println(F("Connecting to MQTT..."));
-  int8_t ret;
-  while ((ret = mqtt.connect()) != 0) {
-       switch (ret) {
-          case 1: Serial.println(F("Wrong protocol")); break;
-          case 2: Serial.println(F("ID rejected")); break;
-          case 3: Serial.println(F("Server unavail")); break;
-          case 4: Serial.println(F("Bad user/pass")); break;
-          case 5: Serial.println(F("Not authed")); break;
-          case 6: Serial.println(F("Failed to subscribe")); break;
-          default: Serial.println(F("Couldn't connect to MQTT server")); break;
-       }
-       Serial.println(F("Retrying MQTT connection"));
-       mqtt.disconnect();
-       delay(5000); 
-  }
-  Serial.println(F("MQTT Connected!"));
 }
 
 uint32_t x=0;
 
 void loop() {
+  // Ensure the connection to the MQTT server is alive (this will make the first
+  // connection and automatically reconnect when disconnected).  See the MQTT_connect
+  // function definition further below.
+  MQTT_connect();
+
   // Try to ping the MQTT server
   /*
   if (! mqtt.ping(3) ) {
@@ -134,3 +120,34 @@ void loop() {
 
   delay(1000);
 }
+
+// Function to connect and reconnect as necessary to the MQTT server.
+// Should be called in the loop function and it will take care if connecting.
+void MQTT_connect() {
+  int8_t ret;
+
+  // Stop if already connected.
+  if (mqtt.connected()) {
+    return;
+  }
+
+  Serial.print("Connecting to MQTT... ");
+
+  while ((ret = mqtt.connect()) != 0) { // connect will return 0 for connected
+       switch (ret) {
+          case 1: Serial.println("Wrong protocol"); break;
+          case 2: Serial.println("ID rejected"); break;
+          case 3: Serial.println("Server unavailable"); break;
+          case 4: Serial.println("Bad user/password"); break;
+          case 5: Serial.println("Not authenticated"); break;
+          case 6: Serial.println("Failed to subscribe"); break;
+          default: Serial.print("Couldn't connect to server, code: ");
+                   Serial.println(ret);
+                   break;
+       }
+       Serial.println("Retrying MQTT connection in 5 seconds...");
+       mqtt.disconnect();
+       delay(5000);  // wait 5 seconds
+  }
+  Serial.println("MQTT Connected!");
+}