Message Queuing Telemetry Transport Client

Please click on the ‘Code’ and ‘Video’ buttons displayed above to view project source code and the application in action!

Abstract

The MQTT protocol is a machine-to-machine (M2M)/Internet of Things connectivity protocol. Designed as an extremely lightweight publish/subscribe messaging transport, it is useful for connections with remote locations where a small code footprint is required and/or network bandwidth is at a premium.

Connection Details

Description

The MQTT client application is built using Python & Eclipse Paho MQTT Client library.

The application respects the following protocol:

1. Connect to the broker.

2. Send a message containing User ID to the topic ‘login’.

   Example:
   Topic = ‘login’
   Message = ‘12345’

3. Once we have sent the message to ‘login’, we shall receive a message on the topic ‘User ID/UUID’. The message will contain a UNIQUE ID.

   Example:
   Topic = ‘12345/UUID’
   Message = ‘1234-fdsfs-12441-qa241’

4. After 3 seconds from the publishing of the UNIQUE ID by the broker, we start receiving multiple messages/commands on the topic ‘UNIQUE ID’ with different commands.

   Example:
   Topic = ‘1234-fdsfs-12441-qa241’
   Message = ‘CMD1’

5. For each command we should send a specific reply (check the commands and the replies below) to the following topic: ‘UNIQUE ID/CMD’.

   Command	Expected Reply
   CMD1	Apple
   CMD2	Cat
   CMD3	Dog
   CMD4	Rat
   CMD5	Boy
   CMD6	Girl
   CMD7	Toy

   Example:
   Topic = ‘1234-fdsfs-12441-qa241/CMD1’
   Message = ‘Apple’

6. Once all the commands are handled and replies are sent (respecting the Quality of Service (QOS) level), we shall receive the following message from broker: ‘Well done my IoT!’ on the topic ‘UNIQUE ID’.

   Example:
   Topic = ‘1234-fdsfs-12441-qa241/CMD1’
   Message = ‘Apple’

7. Once we receive this message, the communcation is over and we can disconnect from the broker.

   Note:
   We will receive a random number of commands from the list above. They can come repeatedly and in any order. There will be no more commands after the final message is received!

Requirements

1. paho-mqtt

   To run the code, you must install Python 3 & the above packages can be installed by running the below command:

   pip install -r requirements.txt

Execution Steps

1. Clone the repository to your computer/raspberry pie.
2. Run MQTT Client: ‘python mqtt_client.py’.

References

1. MQTT Essential Series

Author

Akshay Joshi