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create a directory MQTT

Code Block

language	bash

sudo mkdir MQTT
cd MQTT/

Download the mosquitto from this site or simply use the following command. http://mosquitto.org/download/

Code Block

language	bash

sudo wget http://mosquitto.org/files/source/mosquitto-1.0.2.tar.gz

I used this mosquitto-1.0.2.tar.gz version for this tutorial

Follow these commands to install mosquitto

Code Block

language	bash

sudo apt-get install libwrap0-dev
tar zxf mosquitto-1.0.2.tar.gz
cd mosquitto-1.0.2/
make
sudo make install
sudo ldconfig
sudo make clean
sudo iptables -A INPUT -p tcp -m tcp --dport 1883 -j ACCEPT

If it fails the compile process try the following supportive commands on the terminal to install the dependency libraries. Then compile again

Code Block

language	bash

sudo apt-get install libssl-dev
sudo apt-get install python-mosquitto

Next step is to prepare the MQTT client script to communicate with gadgetkeeper MQTT server. Following Python script can be used to do it. First go to the gadgetkeeper directory we created on the Temperature monitoring with BeagleBoneBlack and DHT11/22 and AM2302 temperature and humidity sensor tutorial. Then create a file as follows

Code Block

language	bash

cd /root/gadgetkeeper/
sudo nano mqtt_listner.py

Then paste the following Python code on it.

Code Block

language	py

#!/usr/bin/python
import time
import mosquitto
import random
import commands
###############################################
 
# change this thing ID as required
THING_ID="ecf5ceb002d111e49e72fb53d9d5a540"
BROKER_NAME="devapi.gadgetkeeper.com"
READ_TEMP="python /root/gadgetkeeper/read_temperature.py 11 30"
READ_HUMID="python /root/gadgetkeeper/read_humidity.py 11 30"
###############################################
 
topic = 'thing.' + THING_ID
broker = BROKER_NAME
client_name = "device-1"
last_id = ""
def on_message(mosq, obj, msg):
    global last_id
    print 'Request: ' +  msg.payload
    id,jsn,cmd = msg.payload.split(',', 2 );
    #print id
    #print jsn
    #print cmd
    if last_id == id:
        print 'Update successful'
        return
    last_id = id
    #data_val = 20.00
    #data_val = random.uniform(1.5, 100.9) #genarate random value for testing
    #read temperature from the sensor
    data_value = commands.getoutput(READ_TEMP)
#    data_value = commands.getoutput(READ_HUMID)
    if 'Failed' not in data_value:
        data_val = data_value[26:]
#       data_val = data_value[23:] 
        print 'Sensor reading: ' + data_val
    else:
        time.sleep(2) #delay 2s and try again
        data_val = commands.getoutput(READ_TEMP)
#       data_val = commands.getoutput(READ_HUMID)
    if 'Failed' in data_value:
        data_val = -1000.0 # If sensor reading fails assign this value
        print 'Sensor read error'
    reply_msg = id + ',' + jsn + ',' + "\"result\":" + str(data_val) + '}'
    print 'Response: ' + reply_msg
    client_rply = mosquitto.Mosquitto("device-1")
    client_rply.connect(broker)
    client_rply.publish(topic, reply_msg ,0)
client = mosquitto.Mosquitto(client_name)
client.connect(broker)
client.subscribe(topic,0)
client.on_message = on_message
while True:
    client.loop(15)
    time.sleep(2)

Now simply run this script as follows

Code Block

language	bash

sudo python mqtt_listner.py

Make sure that port 1883 is not blocked by the firewall.

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