Update MQTT examples

- Update the discerptions
- Clear warnings

Arduino_package/hardware/libraries/MQTTClient/examples/MQTT_Auth/MQTT_Auth.ino

@@ -1,22 +1,21 @@
 /*
- Basic MQTT example with Authentication
-
-  - connects to an MQTT server, providing username
-    and password
+ MQTT Authentication example
+  - connects to an MQTT server, providing username and password
   - publishes "hello world" to the topic "outTopic"
   - subscribes to the topic "inTopic"
-*/
+
+ Example guide:
+ https://www.amebaiot.com/en/amebad-arduino-mqtt-upload-listen/
+ */
 
 #include <WiFi.h>
 #include <PubSubClient.h>
 
-// Update these with values suitable for your network.
 char ssid[] = "Network_SSID";       // your network SSID (name)
 char pass[] = "Password";           // your network password
 int status = WL_IDLE_STATUS;        // Indicater of Wifi status
 
-char mqttServer[] = "cloud.amebaiot.com";
-
+char mqttServer[]     = "cloud.amebaiot.com";
 char clientId[]       = "amebaClient";
 char clientUser[]     = "testuser";
 char clientPass[]     = "testpass";
@@ -25,18 +24,27 @@ char publishPayload[] = "hello world";
 char subscribeTopic[] = "inTopic";
 
 void callback(char* topic, byte* payload, unsigned int length) {
-    // handle message arrived
+    Serial.print("Message arrived [");
+    Serial.print(topic);
+    Serial.print("] ");
+    for (unsigned int i = 0; i < length; i++) {
+        Serial.print((char)(payload[i]));
+    }
+    Serial.println();
 }
 
 WiFiClient wifiClient;
 PubSubClient client(mqttServer, 1883, callback, wifiClient);
 
 void setup() {
+    //Initialize serial and wait for port to open:
     Serial.begin(115200);
+    // wait for serial port to connect.
     while (!Serial) {
         ;
     }
 
+    //Attempt to connect to WiFi network
     while (status != WL_CONNECTED) {
         Serial.print("Attempting to connect to SSID: ");
         Serial.println(ssid);

Arduino_package/hardware/libraries/MQTTClient/examples/MQTT_Basic/MQTT_Basic.ino

@@ -1,12 +1,11 @@
 /*
 
- Basic MQTT example
+ MQTT Basic example
 
  This sketch demonstrates the basic capabilities of the library.
- It connects to an MQTT server then:
+  - connects to an MQTT server
   - publishes "hello world" to the topic "outTopic"
-  - subscribes to the topic "inTopic", printing out any messages
-    it receives. NB - it assumes the received payloads are strings not binary
+  - subscribes to the topic "inTopic", printing out any messages it receives. It assumes the received payloads are strings not binary
 
  It will reconnect to the server if the connection is lost using a blocking
  reconnect function. See the 'mqtt_reconnect_nonblocking' example for how to
@@ -33,7 +32,7 @@ void callback(char* topic, byte* payload, unsigned int length) {
     Serial.print("Message arrived [");
     Serial.print(topic);
     Serial.print("] ");
-    for (int i = 0; i < length; i++) {
+    for (unsigned int i = 0; i < length; i++) {
         Serial.print((char)(payload[i]));
     }
     Serial.println();
@@ -45,7 +44,7 @@ PubSubClient client(wifiClient);
 void reconnect() {
     // Loop until we're reconnected
     while (!(client.connected())) {
-        Serial.print("Attempting MQTT connection...");
+        Serial.print("\nAttempting MQTT connection...");
         // Attempt to connect
         if (client.connect(clientId)) {
             Serial.println("connected");

Arduino_package/hardware/libraries/MQTTClient/examples/MQTT_Publish_In_Callback/MQTT_Publish_In_Callback.ino

@@ -1,7 +1,6 @@
 /*
- Publishing in the callback
-
-  - connects to an MQTT server
+ MQTT Publishing in the callback
+  - connects to an MQTT server, providing username and password
   - subscribes to the topic "inTopic"
   - when a message is received, republishes it to "outTopic"
 
@@ -12,12 +11,13 @@
   This ensures the client reference in the callback function
   is valid.
 
-*/
+ Example guide:
+ https://www.amebaiot.com/en/amebad-arduino-mqtt-upload-listen/
+ */
 
 #include <WiFi.h>
 #include <PubSubClient.h>
 
-// Update these with values suitable for your network.
 char ssid[] = "Network_SSID";       // your network SSID (name)
 char pass[] = "Password";           // your network password
 int status = WL_IDLE_STATUS;        // Indicater of Wifi status
@@ -30,14 +30,18 @@ char publishTopic[]   = "outTopic";
 char publishPayload[] = "hello world";
 char subscribeTopic[] = "inTopic";
 
-// Callback function header
 void callback(char* topic, byte* payload, unsigned int length);
 
 WiFiClient wifiClient;
 PubSubClient client(mqttServer, 1883, callback, wifiClient);
 
 // Callback function
 void callback(char* topic, byte* payload, unsigned int length) {
+    Serial.print("Message arrived [");
+    Serial.print(topic);
+    Serial.print("] ");
+    Serial.println();
+
     // In order to republish this payload, a copy must be made
     // as the orignal payload buffer will be overwritten whilst
     // constructing the PUBLISH packet.
@@ -52,11 +56,14 @@ void callback(char* topic, byte* payload, unsigned int length) {
 }
 
 void setup() {
+    //Initialize serial and wait for port to open:
     Serial.begin(115200);
+    // wait for serial port to connect.
     while (!Serial) {
         ;
     }
 
+    //Attempt to connect to WiFi network
     while (status != WL_CONNECTED) {
         Serial.print("Attempting to connect to SSID: ");
         Serial.println(ssid);