Arduino and MQTT

I guess more specifically, looking at this bit:

void callback(char* topic, byte* payload, unsigned int length) {

  // handle message arrived

}

And this bit:

void setup()

{

  Ethernet.begin(mac, ip);

  if (client.connect("arduinoClient")) {

    client.publish("outTopic","hello world");

    client.subscribe("inTopic");

  }

}

I assume if I wish to turn on an led I'd write :

digitalwrite (ledPin, HIGH0;

inside the curly braces of the first bit

and from the second bit I assume it's subscribing to the topic "inTopic"

but how do I define the Message at which the led would turn on?

the example you provide has no setup of the callback, do you have some code missing or not posted ?

Can you post the complete sketch so I can see what your doing

Thanks

Here is the complete sketch, it's just the example provided from the library with a few minor alterations:

/*

Basic MQTT example

 

  - connects to an MQTT server

  - publishes "hello world" to the topic "outTopic"

  - subscribes to the topic "inTopic"

*/

 

 

#include <SPI.h>

#include <Ethernet.h>

#include <PubSubClient.h>

int ledPin = 5;

 

 

// Update these with values suitable for your network.

byte mac[]    = {  0xDE, 0xED, 0xBA, 0xFE, 0xFE, 0xED };

byte server[] = { 192, 168, 1, 199 };

byte ip[]     = { 192, 168, 1, 50 };

 

 

void callback(char* topic, byte* payload, unsigned int length) {

  // handle message arrived

}

 

 

EthernetClient ethClient;

PubSubClient client(server, 1883, callback, ethClient);

 

 

void setup()

{

  Ethernet.begin(mac, ip);

  if (client.connect("arduinoClient")) {

    client.publish("outTopic","hello world");

    client.subscribe("inTopic");

  }

}

 

 

void loop()

{

  client.loop();

}

Do you have a server configured somewhere ?, this is a client example and in that is ok, but it needs to talk to an MQTT Server in order for  all this to work

I am currently playing with MQTT servers with the SAMA5D3 boards and have no issues but you do need the server and he client for it all to work

Yes, I have a Broker set up on my server at 192.168.1.199.

I have an mqtt client on my android phone and a client on my computer. I can send mqtt messages from either device and receive mqtt messages from subscribed topics on either device.

I have another sketch that sends mqtt message on a button press and that works well, but right now I'm trying to learn how to execute an action when a specific message is received from the subscribed topic.

ah, well this may help then

http://www.element14.com/community/groups/arduino/blog/2014/06/09/fast-track-to-arduino-programming

a series of videos for the arduino and the one for Ethernet deals with interpreting messages received from the network

Hoe you find it useful

Peter

Thank you very Much, Really appreciate it, just started looking and I can already tell this will help a lot. Really appreciate it!

Seriously, really thank you. I have much better understanding now.

your welcome

Peter