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Mosquitto

Eclipse Mosquitto is an open source (EPL/EDL licensed) message broker that implements the MQTT protocol versions 5.0, 3.1.1 and 3.1. Mosquitto is lightweight and is suitable for use on all devices from low power single board computers to full servers.

The MQTT protocol provides a lightweight method of carrying out messaging using a publish/subscribe model. This makes it suitable for Internet of Things messaging such as with low power sensors or mobile devices such as phones, embedded computers or microcontrollers.

The Mosquitto project also provides a C library for implementing MQTT clients, and the very popular mosquitto_pub and mosquitto_sub command line MQTT clients.

For more information see https://mosquitto.org

Installation

sudo apt-get install mosquitto
sudo apt-get install mosquitto-clients

Usage

sudo service mosquitto stop

sudo service mosquitto start

Configuration

Default configuration can be found at:

/etc/mosquitto/mosquitto.conf

Example config file can be found at:

/usr/share/doc/mosquitto/examples/mosquitto.conf.example

Custom config file needs to be placed at

/etc/mosquitto/conf.d/

Password file

Create a new password file

# Create empty password file
touch /etc/mosquitto/mosquitto_passwd
# Fill password file
mosquitto_passwd -c /etc/mosquitto/mosquitto_passwd username password

To add a new user to the existing password file use:

mosquitto_passwd -b /etc/mosquitto/mosquitto_passwd username password

For activating the passwordfile you need to create a custom config file /etc/mosquitto/conf.d/mosquitto.conf and att the following lines:

allow_anonymous false
password_file /etc/mosquitto/mosquitto_passwd

Python example

More informations at http://www.steves-internet-guide.com/client-connections-python-mqtt/

Install the paho-mqtt library

sudo pip3 install paho-mqtt

import paho.mqtt.client as mqtt

# connection callback
def on_connect(client, userdata, flags, rc):
   print("Connected with result code " + str(rc))

# message received callback
def on_message(client, userdata, msg):
   print(msg.topic + " " + str(msg.payload))
   client.publish("/out", "received an input...")

# set up the client
client = mqtt.Client()
client.on_connect = on_connect
client.on_message = on_message
client.connect("mqtt.eclipse.org", 1883, 60) # address ip, port number, keep alive

# subscribe
client.subscribe("/in")

# process the MQTT business
client.loop_forever()

Paho Return Codes

Connection Return Codes

  • 0: Connection successful
  • 1: Connection refused -- incorrect protocol version
  • 2: Connection refused -- invalid client identifier
  • 3: Connection refused -- server unavailable
  • 4: Connection refused -- bad username or password
  • 5: Connection refused -- not authorised
  • 6-255: Currently unused.