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.

Revision:
2:638c854c0695
Parent:
1:a1d5c7a6acbc
Child:
3:7a6a899de7cc
diff -r a1d5c7a6acbc -r 638c854c0695 main.cpp
--- a/main.cpp	Wed Feb 05 10:50:15 2014 +0000
+++ b/main.cpp	Wed Apr 30 13:16:09 2014 +0000
@@ -13,77 +13,198 @@
  * Contributors:
  *    Ian Craggs - initial API and implementation and/or initial documentation
  *******************************************************************************/
+ 
+ /**
+  This is a sample program to illustrate the use of the MQTT Client library
+  on the mbed platform.  The Client class requires two classes which mediate
+  access to system interfaces for networking and timing.  As long as these two
+  classes provide the required public programming interfaces, it does not matter
+  what facilities they use underneath. In this program, they use the mbed
+  system libraries.
+ 
+ */
 
 #include "mbed.h"
 #include "EthernetInterface.h"
+
 #include "C12832_lcd.h"
-
-#include "MQTTPacket.h"
-
-DigitalOut myled(LED2);
 C12832_LCD lcd;
 
-int publish()
+#include "FP.cpp"
+#include "MQTTClient.h"
+
+
+
+class IPStack 
 {
-    MQTTPacket_connectData data = MQTTPacket_connectData_initializer;
-    int rc = 0;
-    char buf[200];
-    int buflen = sizeof(buf);
+public:    
+    IPStack()
+    {
+        eth.init();                          // Use DHCP
+        eth.connect();
+        mysock.set_blocking(false, 1000);    // 1 second Timeout 
+    }
+    
+    int connect(char* hostname, int port)
+    {
+        return mysock.connect(hostname, port);
+    }
+
+    int read(char* buffer, int len, int timeout)
+    {
+        mysock.set_blocking(false, timeout);  
+        return mysock.receive(buffer, len);
+    }
+    
+    int write(char* buffer, int len, int timeout)
+    {
+        mysock.set_blocking(false, timeout);  
+        return mysock.send(buffer, len);
+    }
+    
+    int disconnect()
+    {
+        return mysock.close();
+    }
+    
+private:
+
+    EthernetInterface eth;
     TCPSocketConnection mysock; 
-    MQTTString topicString = MQTTString_initializer;
-    char* payload = "I'm alive!";
-    int payloadlen = strlen(payload);
-    int len = 0;
+    
+};
+
+
+class Countdown
+{
+public:
+    Countdown()
+    {
+        t = Timer();   
+    }
+    
+    Countdown(int ms)
+    {
+        t = Timer();
+        countdown_ms(ms);   
+    }
+    
     
-    mysock.connect("m2m.eclipse.org", 1883);
-          
-    data.clientID.cstring = "mbed test client - Ian Craggs";
-    data.keepAliveInterval = 20;
-    data.cleansession = 1;
-    data.MQTTVersion = 3;
-
-    len = MQTTSerialize_connect(buf, buflen, &data);
+    bool expired()
+    {
+        return t.read_ms() >= interval_end_ms;
+    }
+    
+    void countdown_ms(int ms)  
+    {
+        t.stop();
+        interval_end_ms = ms;
+        t.reset();
+        t.start();
+    }
+    
+    void countdown(int seconds)
+    {
+        countdown_ms(seconds * 1000);
+    }
+    
+    int left_ms()
+    {
+        return interval_end_ms - t.read_ms();
+    }
+    
+private:
+    Timer t;
+    int interval_end_ms; 
+};
 
-    topicString.cstring = "mbed NXP LPC1768";
-    len += MQTTSerialize_publish(buf + len, buflen - len, 0, 0, 0, 0, topicString, payload, payloadlen);
+int arrivedcount = 0;
+
+void messageArrived(MQTT::Message* message)
+{
+    lcd.printf("Message arrived: qos %d, retained %d, dup %d, packetid %d\n", message->qos, message->retained, message->dup, message->id);
+    lcd.printf("Payload %.*s\n", message->payloadlen, (char*)message->payload);
+    ++arrivedcount;
+}
 
-    len += MQTTSerialize_disconnect(buf + len, buflen - len);
+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;
+    char* topic = "mbed-sample";
+    
+    lcd.printf("Version is %f\n", version);
+              
+    MQTT::Client<IPStack, Countdown>client = MQTT::Client<IPStack, Countdown>(&ipstack);
 
-    rc = 0;
-    while (rc < len)
-    {
-        int rc1 = mysock.send(buf, len);
-        if (rc1 == -1)
-        {
-            lcd.printf("Send failed\n");
-            break;
-        }
-        else
-            rc += rc1;
-    }
-    if (rc == len)
-        lcd.printf("Send succeeded\n");
-    wait(0.2);
+    MQTT::Client<IPStack, Countdown>::connectionLostInfo info = {&client, &ipstack};
+    int rc = connect(&info);
+    
+    client.setConnectionLostHandler(connect);
+    
+    rc = client.subscribe(topic, MQTT::QOS1, messageArrived);   
+    if (rc != 0)
+        lcd.printf("rc from MQTT subscribe is %d\n", rc);
+
+    MQTT::Message message;
 
+    // QoS 0
+    char buf[100];
+    sprintf(buf, "Hello World!  QoS 0 message from app version %f\n", version);
+    message.qos = MQTT::QOS0;
+    message.retained = false;
+    message.dup = false;
+    message.payload = (void*)buf;
+    message.payloadlen = strlen(buf)+1;
+    rc = client.publish(topic, &message);
+    while (arrivedcount == 0)
+        client.yield(100);
+        
+    // QoS 1
+    sprintf(buf, "Hello World!  QoS 1 message from app version %f\n", version);
+    message.qos = MQTT::QOS1;
+    message.payloadlen = strlen(buf)+1;
+    rc = client.publish(topic, &message);
+    while (arrivedcount == 1)
+        client.yield(100);
+        
+    // QoS 2
+    sprintf(buf, "Hello World!  QoS 2 message from app version %f\n", version);
+    message.qos = MQTT::QOS2;
+    message.payloadlen = strlen(buf)+1;
+    rc = client.publish(topic, &message);
+    while (arrivedcount == 2)
+        client.yield(100);
+    
+    rc = client.unsubscribe(topic);
+    if (rc != 0)
+        lcd.printf("rc from unsubscribe was %d\n", rc);
+    
+    rc = client.disconnect();
+    if (rc != 0)
+        lcd.printf("rc from disconnect was %d\n", rc);
+    
+    ipstack.disconnect();
+    
+    lcd.printf("Finishing with %d messages received\n", arrivedcount);
+    
     return 0;
 }
-
-int main()
-{
-    EthernetInterface eth;
-    eth.init(); //Use DHCP
-    eth.connect();
-    lcd.printf("IP Address is %s\n", eth.getIPAddress());
-    
-    while(1) 
-    {
-        myled = 1;
-        publish();
-        wait(0.2);
-        myled = 0;
-        publish();
-        wait(0.2);
-    }
-    
-    eth.disconnect();
-}