Introduction to MQTT#

MQTT is a lightweight messaging protocol originally designed for communication in constrained networks with limited bandwidth and compute resources. Developed with simplicity and scalability in mind, MQTT is particularly well-suited for Internet of Things (IoT) applications where the variety and quantity of devices are growing exponentially.

Official Description of MQTT Specification

“MQTT is a Client Server publish/subscribe messaging transport protocol. It is lightweight, open, simple, and designed so as to be easy to implement. These characteristics make it ideal for use in many situations, including constrained environments such as for communication in Machine to Machine (M2M) and Internet of Things (IoT) contexts where a small code footprint is required and/or network bandwidth is at a premium.”

MQTT uses a binary message format for communication between clients and servers (brokers). This is in contrast to other protocols that use text-based formats, such as HTTP or SMTP.

The binary format used by MQTT is designed to reduce the size of messages and increase the efficiency of communication. By using a binary format, the protocol can minimize the amount of data that needs to be transmitted and reduce the processing power required to interpret messages. This makes MQTT well-suited for use in low-bandwidth or low-power environments, such as IoT devices with limited resources. It’s also used in enterprise systems, where real-time data communication is necessary.

MQTT offers several key benefits:

1. Lightweight and efficient: MQTT minimizes the network bandwidth and compute resources required by clients to exchange data.
2. Bidirectional communication: MQTT allows devices to send data to and receive data from the server, allowing for bidirectional data exchange with other components in the network.
3. Scalable: MQTT can scale to support millions of devices or “things” in an IoT or IIoT ecosystem.
4. Reliable message delivery: MQTT specifies different Quality of Service (QoS) levels to ensure reliable message delivery.
5. Message Buffering and Session Resumption: MQTT supports persistent sessions between devices and servers, enhancing message reliability by ensuring that messages are delivered to clients even after disconnections.
6. Security features: MQTT supports TLS encryption for message confidentiality and authentication protocols for client verification.

Origin and History of MQTT

MQTT was originally developed within IBM, who in 2011, contributed MQTT client implementations to the newly founded Paho project of the Eclipse Foundation.

In 2014, OASIS announced that it would take over the standardization of MQTT, with the goal of making it an open and vendor-neutral protocol.

Basics of MQTT#

At the core of MQTT are MQTT brokers and MQTT clients. The MQTT broker is an intermediary between senders and receivers, dispatching messages to the appropriate recipients. MQTT clients publish messages to the broker, and other clients subscribe to specific topics to receive messages. Each MQTT message includes a topic, and clients subscribe to topics of their interest. The MQTT broker maintains a subscriber list and uses it to deliver messages to the relevant clients.

An MQTT broker can also buffer messages for disconnected clients, ensuring reliable message delivery even in unreliable network conditions.

Use Case Example: An IoT Application Built Using Raspberry Pi, MQTT, and Temperature Sensor#

In this example, we explore the connection of a temperature and brightness sensor to a Raspberry Pi, and then leveraging the power of MQTT to transmit the sensor data to a designated MQTT broker effortlessly. We will discover how another device, acting as a control center, can effortlessly receive and process the MQTT data, enabling efficient monitoring and control of our IoT ecosystem.