[vc_row][vc_column width=”1/1″][vc_column_text]A pcDuino8 Uno makes a really great central hub for small IoT networks. It is very inexpensive, it consumes very little power and it has no fans or other mechanical parts that might cause failure. This post shows you the steps to get up and running with an MQTT broker.

Note: Ubuntu14.04 has been installed on pcDuino8 Uno.

1. Synchronize time

sudo ntpdate us.pool.ntp.org

2. Install Node and npm

Set up the apt-get repo source.

curl -sL https://deb.nodesource.com/setup | sudo -E bash -
sudo apt-get install -y nodejs
sudo ln -s /usr/bin/nodejs /usr/bin/node
sudo apt-get install -y npm
echo "export NODE_PATH=<your local node_modules file path>" >> ~/.bashrc
source ~/.bashrc

Note: Global node_modules file path shuold be /usr/lib/node_modules, or /usr/local/lib/node_moduels/

3. Install required node modules with npm

sudo npm install mosca -g
sudo npm install mqtt -g
sudo npm install daemon -g

4. Write JavaScript code

vim mosca-app.js

mosca-app.js: MQTT-Server code

console.log(process.pid);
//require('daemon')();

var moscaSettings = {
  port: 1883,
  host: "localhost"
};

var server = new mosca.Server(moscaSettings);
server.on('ready', setup);

server.on('clientConnected', function(client) {
    console.log('client connected', client.id);     
});

server.on('published', function(packet, client) {
  console.log('Published', packet.payload);
});

function setup() {
  console.log('Mosca server is up and running')
}
console.log(process.pid);

vim client-pub.js

client-pub.js: MQTT-pub client for test

var mqtt    = require('mqtt');
var client  = mqtt.connect('mqtt://localhost');

client.on('connect', function () {
  client.publish('device/control', 'Hello!', {retain: false, qa: 1});
client.end();
});

vim client-sub.js

client-sub.js: MQTT-sub client for test

var mqtt    = require('mqtt');
var client  = mqtt.connect('mqtt://localhost');

client.on('connect', function () {
  client.subscribe('device/control');

client.on('message', function (topic, message) {
  console.log(message.toString());
client.end();
  });
});

5. Test MQTT Server

Open a terminal:

node mosca-app.js
node client-sub.js   ##Subscribe a message, the topic is 'device/control'

Open another terminal

node client_pub.js ##Publish a message, the topis is 'device/control'

client-sub.js will get a message published from client-pub.js.[/vc_column_text][/vc_column][/vc_row]