Understanding What is MQTT (Message Queuing Telemetry Transport)

MQTT (MQ Telemetry Transport) is a lightweight open messaging protocol that is widely used for machine-to-machine (M2M) communication in low-bandwidth environments. It provides a simple way for resource-constrained network clients to distribute telemetry information. MQTT uses a publish/subscribe communication pattern and is particularly suitable for wireless networks with varying levels of latency and occasional bandwidth constraints. It has become the leading open source protocol for connecting IoT and IIoT devices, although it was originally used in the oil and gas industry for SCADA systems.

Key Takeaways

• MQTT is a lightweight open messaging protocol for machine-to-machine communication in low-bandwidth environments.
• It uses a publish/subscribe communication pattern and is suitable for wireless networks with varying levels of latency and occasional bandwidth constraints.
• MQTT has become the leading open source protocol for connecting IoT and IIoT devices.
• Originally used in the oil and gas industry for SCADA systems.
• Offers a simple way for resource-constrained network clients to distribute telemetry information.

How does MQTT work?

The MQTT protocol operates on a publish/subscribe model, which allows for efficient and flexible communication between MQTT clients. MQTT clients can be either publishers or subscribers, and they interact with an MQTT broker to exchange messages. Publishers send messages to the broker, which acts as an intermediary and routes the messages to the appropriate subscribers. Subscribers, on the other hand, receive the messages they are interested in from the broker.

One of the key advantages of MQTT is its ability to handle multiple clients and topics. Clients can connect to an MQTT broker and subscribe to specific topics, which represent categories or subjects of interest. When a publisher sends a message to a topic, the broker ensures that the message is delivered to all subscribers who have expressed interest in that topic. This publish/subscribe model allows for efficient and scalable communication between connected devices in IoT applications.

To establish communication with the broker, MQTT clients utilize TCP/IP connections. These connections enable reliable and secure data transfer between clients and the broker. In addition, MQTT supports features such as retained messages, where the broker retains the last message published to a topic and delivers it to new subscribers, and the ability for clients to manage disconnects and reconnects seamlessly, ensuring reliable message delivery even in unstable network conditions.

Example Scenario: Smart Home Automation

Let’s consider a scenario of a smart home automation system using MQTT. In this case, the MQTT broker acts as the central hub, while the various devices in the home, such as sensors, lights, and thermostats, are MQTT clients. The sensors would act as publishers, sending real-time data about temperature, humidity, and occupancy to the broker. The lights and thermostats, on the other hand, would subscribe to specific topics to receive commands from the broker. For example, when the occupancy sensor detects movement, it publishes a message to the “occupancy” topic, which triggers the lights to turn on by subscribing to that topic.

MQTT allows for seamless communication between sensors, devices, and applications in an IoT ecosystem, enabling real-time data exchange and efficient control of connected devices.

What is an MQTT broker?

An MQTT broker is a crucial component in the MQTT messaging protocol that facilitates effective message distribution between MQTT clients. Acting as an intermediary, the MQTT broker is responsible for receiving and filtering messages from publishers and distributing them to the appropriate subscribers. This process ensures that messages are delivered efficiently and reliably within an MQTT network.

One of the key functions of an MQTT broker is to identify which clients have subscribed to specific topics and ensure that messages are sent to the relevant subscribers. This allows for flexible and targeted message distribution, enabling clients to receive only the information they are interested in. Additionally, the broker can handle millions of concurrently connected MQTT clients, showcasing its scalability and ability to support large-scale deployments.

Scalability is an essential aspect of an MQTT broker’s performance. The scalability of a broker refers to its capacity to handle a growing number of MQTT clients and efficiently manage message delivery. A highly scalable MQTT broker can accommodate a large number of publishers and subscribers, ensuring seamless communication between devices. This scalability is especially important in IoT applications, where numerous devices may be connected to the network and need to exchange real-time data.

Benefits of using an MQTT broker:

• Efficient message distribution: An MQTT broker efficiently routes messages to the appropriate subscribers, ensuring that clients receive the information they need.
• Scalability: MQTT brokers can handle millions of concurrently connected clients, making them suitable for large-scale IoT deployments.
• Reliable message delivery: The broker plays a critical role in ensuring that messages are reliably delivered, even in the presence of intermittent network connectivity.
• Flexible topic-based communication: MQTT brokers enable clients to subscribe to specific topics of interest, allowing for targeted message distribution.

The MQTT broker is an integral part of the MQTT protocol, providing the necessary infrastructure for efficient and reliable message distribution in IoT applications. Its ability to handle large numbers of clients and effectively route messages makes it a crucial component in building robust and scalable MQTT networks.

Types of MQTT Messages

In an MQTT session, there are several types of messages that clients can send and receive. These messages are essential for establishing connections, transmitting data, and maintaining communication with the MQTT broker.

Publish

The publish message is used by MQTT clients to send data to a specific topic on the broker. It contains the payload, which can be any type of data, and includes the topic to which the message is published. The broker then distributes the message to all subscribed clients who are interested in receiving data on that topic. This allows for efficient and targeted communication between clients.

Subscribe

The subscribe message allows clients to express their interest in receiving messages on specific topics. Clients can subscribe to multiple topics, and the broker will forward any messages published to those topics to the subscribed clients. This enables clients to receive relevant data and stay updated on the information they require.

Unsubscribe

The unsubscribe message is used by clients to cancel their subscription to a specific topic. When a client unsubscribes from a topic, the broker will no longer forward messages published to that topic to the client. This allows clients to control the flow of data they receive and manage their subscriptions based on changing needs or preferences.

Ping

The ping message is used to maintain the connection between the client and the broker. It acts as a keep-alive mechanism, ensuring that the connection remains active and preventing it from being terminated due to inactivity. The client sends a ping message to the broker, and if a response is received within a specified time period, the connection is considered alive.

Table: MQTT Message Types

By utilizing these different types of MQTT messages, clients can establish connections, exchange data, and ensure a reliable and efficient communication flow within an MQTT network.

What are the Benefits of Using MQTT?

When it comes to IoT applications, MQTT offers a range of benefits that make it a popular choice for efficient and reliable communication. Let’s take a look at some of the key advantages:

Lightweight Protocol

MQTT is designed to be lightweight and efficient, making it ideal for devices with limited resources or low-bandwidth environments. Its simplicity allows for minimal overhead, reducing the strain on both the device and the network. This makes MQTT a perfect fit for IoT devices that need to operate efficiently while conserving energy and resources.

Efficient Data Transmission

One of the major advantages of MQTT is its ability to optimize data transmission. By using a publish/subscribe model, MQTT only sends data to the devices that are subscribed to the corresponding topics. This efficient approach minimizes network usage by reducing unnecessary data transmission, resulting in reduced bandwidth requirements and improved overall system performance.

Low Network Usage

MQTT is designed to work in low-bandwidth and unreliable network conditions. It uses lightweight packet headers and binary payload formats, minimizing the size of the messages exchanged. This reduces the impact on the network and ensures that the available bandwidth is used efficiently. MQTT’s low network usage makes it an excellent choice for applications with limited connectivity or data plans.

Reliable Message Delivery

Reliability is crucial in IoT applications, especially when dealing with critical data and real-time communication. MQTT provides three quality of service (QoS) levels to ensure reliable message delivery: at most once, at least once, and exactly once. These levels allow devices and applications to choose the appropriate level of reliability based on their specific requirements, ensuring that messages are delivered successfully with the desired level of assurance.

Overall, MQTT’s lightweight protocol, efficient data transmission, low network usage, and reliable message delivery make it an excellent choice for a wide range of IoT applications. Its simplicity and versatility have contributed to its widespread adoption, making it a key player in the IoT ecosystem.

What are the drawbacks of MQTT?

While MQTT has many advantages, it also has some drawbacks that need to be considered when implementing the protocol. These drawbacks include slower transmit cycles, resource discovery limitations, and security challenges.

One of the drawbacks of MQTT is its slower transmit cycles compared to other protocols like CoAP. This can be a concern when real-time data transmission is crucial. However, it’s important to note that MQTT’s publish/subscribe model is designed for asynchronous communication, making it more suitable for applications that don’t require immediate responses.

Another drawback of MQTT is its resource discovery mechanism. MQTT relies on flexible topic subscription for resource discovery, which can be less stable compared to other protocols that use a more structured and standardized approach. This can lead to difficulties in managing and discovering resources in complex MQTT networks.

Security challenges also exist when using MQTT. While the protocol itself does not provide built-in security features, it can be secured using various methods such as SSL/TLS encryption and authentication mechanisms. However, implementing and managing these security measures can be complex, and ensuring secure communication between MQTT clients and brokers requires careful configuration and monitoring.

In summary, while MQTT is a powerful and widely-used protocol, it does have some limitations. Slower transmit cycles, resource discovery challenges, and security considerations should be taken into account when deciding to use MQTT in IoT applications. By understanding these drawbacks and implementing appropriate solutions, the benefits of MQTT can still be leveraged effectively in many scenarios.

What is the history behind MQTT protocol?

The MQTT protocol has an interesting history that dates back to its invention in 1999. Originally developed for monitoring oil pipelines in the oil and gas industry, MQTT was created as a lightweight messaging protocol designed to handle machine-to-machine communication in low-bandwidth environments. The protocol was initially known as Message Queuing Telemetry Transport (MQTT) due to its association with the IBM MQ Series.

In 2010, IBM released MQTT 3.1 as a free and open protocol, making it accessible to a wider audience. This release played a significant role in the adoption and popularity of MQTT as an open source protocol for connecting IoT devices. MQTT 3.1 was later submitted to OASIS (Organization for the Advancement of Structured Information Standards) for maintenance.

Fast forward to 2019, and MQTT version 5 was introduced by OASIS. This new version brought several enhancements and additional features to the protocol, further solidifying its position as a leading messaging protocol for IoT applications. MQTT version 5 introduced improved error reporting, enhanced message routing options, and support for advanced quality of service levels.

“MQTT has evolved from a proprietary protocol to the widely adopted messaging protocol it is today. Its invention in the oil and gas industry sparked its initial use, but it has since found applications in various industries. The release of MQTT 3.1 as an open protocol and the subsequent introduction of MQTT version 5 have played a crucial role in its widespread adoption and continued development.”

The history of MQTT showcases its evolution from a proprietary protocol to a widely adopted messaging protocol for IoT applications. The continuous development and improvements to MQTT have enabled its versatility and applicability in various industries and use cases.

Conclusion

In summary, MQTT is a robust messaging protocol that has gained significant popularity in IoT applications. It provides a lightweight and efficient solution for machine-to-machine communication, making it an ideal choice for resource-constrained network clients. MQTT offers several benefits, including efficient data transmission, low network usage, and reliable message delivery through multiple quality of service levels. It is also well-supported in various programming languages, making it a versatile option for IoT implementations.

However, MQTT does have its drawbacks. It has slower transmit cycles compared to other protocols, which may not be suitable for real-time applications. Resource discovery in MQTT relies on flexible topic subscription, which can make it challenging to manage large topic trees. Additionally, MQTT lacks built-in security features, and implementing security measures can be complex.

Despite its limitations, MQTT continues to evolve and adapt to the changing needs of IoT applications. It has become the leading open source protocol for connecting IoT devices and has a strong community support. With its lightweight nature and efficient message distribution, MQTT is a valuable tool for enabling seamless communication and data exchange in IoT ecosystems.

Jana

Jana is a public relations specialist and writes about all kinds of software products that make our life easier.