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:
6:e4c690c45021
Parent:
3:7a6a899de7cc
Child:
7:3de634f2d40c
--- a/main.cpp	Tue May 06 09:45:22 2014 +0000
+++ b/main.cpp	Sun May 11 18:52:57 2014 +0000
@@ -127,38 +127,30 @@
     ++arrivedcount;
 }
 
-int connect(MQTT::Client<IPStack, Countdown>::connectionLostInfo* info)
-{
-    char* hostname = "m2m.eclipse.org";
-    int port = 1883;
-    lcd.printf("Connecting to %s:%d\n", hostname, port);
-    int rc = info->network->connect(hostname, port);
-    lcd.printf("rc from TCP connect is %d\n", rc);
- 
-    MQTTPacket_connectData data = MQTTPacket_connectData_initializer;       
-    data.MQTTVersion = 3;
-    data.clientID.cstring = "mbed-icraggs";
-    rc = info->client->connect(&data);
-    lcd.printf("rc from MQTT connect is %d\n", rc);
-    
-    return rc;
-}
-
 
 int main(int argc, char* argv[])
 {   
     IPStack ipstack = IPStack();
-    float version = 0.3;
+    float version = 0.42;
     char* topic = "mbed-sample";
     
     lcd.printf("Version is %f\n", version);
               
     MQTT::Client<IPStack, Countdown> client = MQTT::Client<IPStack, Countdown>(ipstack);
     
-    client.setConnectionLostHandler(connect);
-
-    MQTT::Client<IPStack, Countdown>::connectionLostInfo info = {&client, &ipstack};
-    int rc = connect(&info);
+    char* hostname = "m2m.eclipse.org";
+    int port = 1883;
+    lcd.printf("Connecting to %s:%d\n", hostname, port);
+    int rc = ipstack.connect(hostname, port);
+    if (rc != 0)
+        lcd.printf("rc from TCP connect is %d\n", rc);
+ 
+    MQTTPacket_connectData data = MQTTPacket_connectData_initializer;       
+    data.MQTTVersion = 3;
+    data.clientID.cstring = "mbed-icraggs";
+    rc = client.connect(&data);
+    if (rc != 0)
+        lcd.printf("rc from MQTT connect is %d\n", rc);
     
     rc = client.subscribe(topic, MQTT::QOS1, messageArrived);   
     if (rc != 0)