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.

main.cpp@0:0cae29831d01, 2014-02-04 (annotated)

Committer:
icraggs
Date:
Tue Feb 04 22:38:15 2014 +0000
Revision:
0:0cae29831d01
Child:
1:a1d5c7a6acbc
Sample program for MQTT client

Who changed what in which revision?

UserRevisionLine numberNew contents of line
icraggs 0:0cae29831d01 1 #include "mbed.h"
icraggs 0:0cae29831d01 2 #include "EthernetInterface.h"
icraggs 0:0cae29831d01 3 #include "C12832_lcd.h"
icraggs 0:0cae29831d01 4
icraggs 0:0cae29831d01 5 #include "MQTTPacket.h"
icraggs 0:0cae29831d01 6
icraggs 0:0cae29831d01 7
icraggs 0:0cae29831d01 8 DigitalOut myled(LED2);
icraggs 0:0cae29831d01 9 C12832_LCD lcd;
icraggs 0:0cae29831d01 10
icraggs 0:0cae29831d01 11 int publish()
icraggs 0:0cae29831d01 12 {
icraggs 0:0cae29831d01 13 MQTTPacket_connectData data = MQTTPacket_connectData_initializer;
icraggs 0:0cae29831d01 14 int rc = 0;
icraggs 0:0cae29831d01 15 char buf[200];
icraggs 0:0cae29831d01 16 int buflen = sizeof(buf);
icraggs 0:0cae29831d01 17 TCPSocketConnection mysock;
icraggs 0:0cae29831d01 18 MQTTString topicString = MQTTString_initializer;
icraggs 0:0cae29831d01 19 char* payload = "I'm alive!";
icraggs 0:0cae29831d01 20 int payloadlen = strlen(payload);
icraggs 0:0cae29831d01 21 int len = 0;
icraggs 0:0cae29831d01 22
icraggs 0:0cae29831d01 23 mysock.connect("m2m.eclipse.org", 1883);
icraggs 0:0cae29831d01 24
icraggs 0:0cae29831d01 25 data.clientID.cstring = "mbed test client - Ian Craggs";
icraggs 0:0cae29831d01 26 data.keepAliveInterval = 20;
icraggs 0:0cae29831d01 27 data.cleansession = 1;
icraggs 0:0cae29831d01 28 data.MQTTVersion = 3;
icraggs 0:0cae29831d01 29
icraggs 0:0cae29831d01 30 len = MQTTSerialize_connect(buf, buflen, &data);
icraggs 0:0cae29831d01 31
icraggs 0:0cae29831d01 32 topicString.cstring = "mbed NXP LPC1768";
icraggs 0:0cae29831d01 33 len += MQTTSerialize_publish(buf + len, buflen - len, 0, 0, 0, 0, topicString, payload, payloadlen);
icraggs 0:0cae29831d01 34
icraggs 0:0cae29831d01 35 len += MQTTSerialize_disconnect(buf + len, buflen - len);
icraggs 0:0cae29831d01 36
icraggs 0:0cae29831d01 37 rc = 0;
icraggs 0:0cae29831d01 38 while (rc < len)
icraggs 0:0cae29831d01 39 {
icraggs 0:0cae29831d01 40 int rc1 = mysock.send(buf, len);
icraggs 0:0cae29831d01 41 if (rc1 == -1)
icraggs 0:0cae29831d01 42 {
icraggs 0:0cae29831d01 43 lcd.printf("Send failed\n");
icraggs 0:0cae29831d01 44 break;
icraggs 0:0cae29831d01 45 }
icraggs 0:0cae29831d01 46 else
icraggs 0:0cae29831d01 47 rc += rc1;
icraggs 0:0cae29831d01 48 }
icraggs 0:0cae29831d01 49 if (rc == len)
icraggs 0:0cae29831d01 50 lcd.printf("Send succeeded\n");
icraggs 0:0cae29831d01 51 wait(0.2);
icraggs 0:0cae29831d01 52
icraggs 0:0cae29831d01 53 return 0;
icraggs 0:0cae29831d01 54 }
icraggs 0:0cae29831d01 55
icraggs 0:0cae29831d01 56 int main() {
icraggs 0:0cae29831d01 57 EthernetInterface eth;
icraggs 0:0cae29831d01 58 eth.init(); //Use DHCP
icraggs 0:0cae29831d01 59 eth.connect();
icraggs 0:0cae29831d01 60 lcd.printf("IP Address is %s\n", eth.getIPAddress());
icraggs 0:0cae29831d01 61
icraggs 0:0cae29831d01 62 while(1) {
icraggs 0:0cae29831d01 63 myled = 1;
icraggs 0:0cae29831d01 64 publish();
icraggs 0:0cae29831d01 65 wait(0.2);
icraggs 0:0cae29831d01 66 myled = 0;
icraggs 0:0cae29831d01 67 publish();
icraggs 0:0cae29831d01 68 wait(0.2);
icraggs 0:0cae29831d01 69 }
icraggs 0:0cae29831d01 70
icraggs 0:0cae29831d01 71 eth.disconnect();
icraggs 0:0cae29831d01 72 }