MQTT / Mbed OS HelloMQTT

Sample MQTT program - simple send and receive

Dependencies:   C12832 MQTT

Dependents:   MQTT_G_SENSOR

This program and the MQTT libraries it uses are part of the EclipseTM Paho project; specifically the embedded client.

This example and API are working, but are still in progress. Please give us your feedback.

HelloMQTT is an example of using the MQTT API. The MQTT API is portable across network interface stacks. MQTT is designed to be used with TCP/IP, but any transport with similar characteristics should be suitable.

HelloMQTT uses the NetworkInterface APIs in mbed OS 5 to show how this works. The MQTT library contains an MQTTNetwork.h header, which is a wrapper around the mbed networking interface. To switch between connectivity methods (the default is Ethernet) the easy-connect library is provided in this example application. You can change the connectivity method in mbed_app.json.

Adding new connectivity methods to the program is trivial, as long as they implement the mbed OS 5 NetworkStack API.

Diff: main.cpp

Revision:
17:0811bdbdd78a
Parent:
16:28d062c5522b
Child:
18:07a79d8f01c3
--- a/main.cpp	Mon Oct 06 11:42:25 2014 +0000
+++ b/main.cpp	Mon Jul 27 09:16:08 2015 +0000
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2014 IBM Corp.
+ * Copyright (c) 2014, 2015 IBM Corp.
  *
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
@@ -12,6 +12,7 @@
  *
  * Contributors:
  *    Ian Craggs - initial API and implementation and/or initial documentation
+ *    Ian Craggs - make sure QoS2 processing works, and add device headers
  *******************************************************************************/
  
  /**
@@ -24,9 +25,20 @@
  
  */
 
+#include "C12832.h"
 
-#include "C12832.h"
-C12832 lcd(p5, p7, p6, p8, p11);
+#if defined(TARGET_UBLOX_C027)
+#warning "Compiling for mbed C027"
+#include "C027.h"
+#elif defined(TARGET_LPC1768)
+#warning "Compiling for mbed LPC1768"
+#include "LPC1768.h"
+#elif defined(TARGET_K64F)
+#warning "Compiling for mbed K64F"
+#include "K64F.h"
+#endif
+
+#define MQTTCLIENT_QOS2 1
 
 #include "MQTTEthernet.h"
 #include "MQTTClient.h"
@@ -37,11 +49,10 @@
 void messageArrived(MQTT::MessageData& md)
 {
     MQTT::Message &message = md.message;
-    lcd.cls();
-    lcd.locate(0,3);
     printf("Message arrived: qos %d, retained %d, dup %d, packetid %d\n", message.qos, message.retained, message.dup, message.id);
     printf("Payload %.*s\n", message.payloadlen, (char*)message.payload);
     ++arrivedcount;
+    lcd.cls();
     lcd.puts((char*)message.payload);
 }
 
@@ -49,20 +60,24 @@
 int main(int argc, char* argv[])
 {   
     MQTTEthernet ipstack = MQTTEthernet();
-    float version = 0.47;
+    float version = 0.5;
     char* topic = "mbed-sample";
     
-    lcd.printf("Version is %f\n", version);
-    printf("Version is %f\n", version);
+    lcd.cls();
+    lcd.printf("HelloMQTT: version is %f\n", version);
               
     MQTT::Client<MQTTEthernet, Countdown> client = MQTT::Client<MQTTEthernet, Countdown>(ipstack);
     
     char* hostname = "m2m.eclipse.org";
     int port = 1883;
+    lcd.cls();
     lcd.printf("Connecting to %s:%d\n", hostname, port);
     int rc = ipstack.connect(hostname, port);
     if (rc != 0)
+    {
+        lcd.cls(); 
         lcd.printf("rc from TCP connect is %d\n", rc);
+    }
  
     MQTTPacket_connectData data = MQTTPacket_connectData_initializer;       
     data.MQTTVersion = 3;
@@ -70,10 +85,16 @@
     data.username.cstring = "testuser";
     data.password.cstring = "testpassword";
     if ((rc = client.connect(data)) != 0)
+    {
+        lcd.cls();
         lcd.printf("rc from MQTT connect is %d\n", rc);
+    }
     
     if ((rc = client.subscribe(topic, MQTT::QOS1, messageArrived)) != 0)
+    {
+        lcd.cls();
         lcd.printf("rc from MQTT subscribe is %d\n", rc);
+    }
 
     MQTT::Message message;
 
@@ -104,30 +125,23 @@
     rc = client.publish(topic, message);
     while (arrivedcount < 3)
         client.yield(100);
-        
-    // n * QoS 2
-    for (int i = 1; i <= 10; ++i)
+            
+    if ((rc = client.unsubscribe(topic)) != 0)
     {
-        sprintf(buf, "Hello World!  QoS 2 message number %d from app version %f\n", i, version);
-        message.qos = MQTT::QOS2;
-        message.payloadlen = strlen(buf)+1;
-        rc = client.publish(topic, message);
-        while (arrivedcount < i + 3)
-            client.yield(100);
+        lcd.cls();
+        lcd.printf("rc from unsubscribe was %d\n", rc);
     }
     
-    if ((rc = client.unsubscribe(topic)) != 0)
-        printf("rc from unsubscribe was %d\n", rc);
-    
     if ((rc = client.disconnect()) != 0)
-        printf("rc from disconnect was %d\n", rc);
+    {
+        lcd.cls();
+        lcd.printf("rc from disconnect was %d\n", rc);
+    }
     
     ipstack.disconnect();
     
     lcd.cls();
-    lcd.locate(0,3);
     lcd.printf("Version %.2f: finish %d msgs\n", version, arrivedcount);
-    printf("Finishing with %d messages received\n", arrivedcount);
     
     return 0;
 }