MQTT: A messaging protocol for the IoT
MQTT (Message Queuing Telemetry Transport) is a lightweight pub-sub messaging protocol used for communication between IoT devices. It is designed for networks with limited bandwidth, high latency, and unpredictable connectivity.
“The ability to simplify means to eliminate the unnecessary so that the necessary may speak.” Hans Hofmann
In modern business, data is king. Analyzing data provides valuable insight and affects the way business is conducted. In industries such as manufacturing, mining, oil & gas, and agriculture, companies use a large number of sensors to analyze trends and improve operations.
By using MQTT, multiple devices can send data to an IT infrastructure. This makes it ideal for remote monitoring, especially in M2M connections which require a small code footprint or where bandwidth is constrained. The MQTT protocol has enabled various businesses to make smarter business decisions using data that was previously left at remote locations. MQTT's features make it an ideal choice for sending large volumes of sensor data to analytics platforms and cloud-based solutions.
What is a Network Protocol, and How does MQTT differ from others?
Protocols determine how data between devices within a network is transmitted. Modern digital communications rely on it to communicate between connected devices. LANs and WANs, as they exist today, rely on network protocols.
Who Uses Network Protocols?
Millions of people use network protocols every day. When people access the internet, they use network protocols, even if they don't understand how network protocols function.
Common Network Protocols:
Hypertext Transfer Protocol (HTTP). This Protocol specifies how to transmit the data across the internet and how web servers and browsers should respond to commands.
Secure Socket Shell (SSH): Even if a computer is connected to an insecure network, this protocol ensures secure access. SSH is very handy for network managers who remotely administer several servers.
Short Message Service (SMS): Messages are delivered and received via this protocol over cellular networks. Sending pictures, videos, and other media requires the Multimedia Messaging Service (MMS), an extension of SMS.
Now, what is MQTT?
This machine-to-machine (M2M) messaging protocol is used for devices with low or unreliable network bandwidth. MQTT has contributed to the rise of both the Internet of Things (IoT) and the Industrial Internet of Things (IIoT).
How does it work?
Clients and Brokers are two different systems defined by the MQTT protocol. A sender (publisher) and a consumer (subscriber) are two types of clients. Devices send topics to ‘broker’. Broker transmits those messages to all devices that have signed up for that topic. The publisher and subscriber are not in direct communication.
Client. A client can be a publisher, a subscriber, or both. Clients use brokers to exchange information. Clients could be an IoT sensor in the field or a server in a data center.
Broker. The broker distributes the information to potential clients. The broker receives all messages, filters them, determines the subscribers, and then sends the message to subscribers.
Topic. The subject of the message. On a topic, clients can either publish or subscribe. The subscriber client will listen for incoming messages and respond to them, such as "on" or "off."
Clients can subscribe to one topic while also publishing to another. If a client subscribes to "LivingRoom/Light," it may also want to publish to a different topic, such as "LivingRoom/Light/State," to inform other clients about the light's status.
Publish. It is the client's information to the broker to distribute to interested clients.
Subscribe. The broker shares the subscribed topic to the clients.
Lightweight and Efficient
MQTT clients are light and can be run on the microcontrollers. MQTT message headers are relatively small to save bandwidth on the network.
MQTT enables device-to-cloud and cloud-to-device communication. This scales to connect with millions of IoT devices.
Reliable Message Delivery
It offers a dependable message delivery system, which is critical in many IoT scenarios.
Supports in Unstable Network
Many IoT devices depend on weak cellular networks to communicate. The architecture of MQTT minimizes the time to connect a client to a broker.
MQTT encrypts messages with TLS and authenticates clients via OAuth or other modern authentication methods.
MQTT was originally designed for the oil and gas industry's low-bandwidth, high-latency data lines. However, The MQTT protocol is also well suited for industrial control systems. Nowadays, services like Facebook Messenger and AWS IoT are using the MQTT protocol. Its high acceptance rate would continue to rise in the future.
Advantages over HTTP
The HTTP request and response pattern have some limitations:
HTTP is a synchronous protocol. The client awaits a response from the server. This is a requirement for web browsers, and it comes at the expense of scalability. With IoT, synchronous communication is difficult due to the large number of devices connected and, especially, in unstable/high latency networks.
MQTT is an asynchronous communications protocol that is better suited for Internet of Things (IoT) applications. The sensors can communicate data to the network, which allows it to determine the best route and timing for delivery to its destination clients and services.
HTTP is one-way. The client must initiate the connection while using HTTP. Devices or sensors in IoT applications are often clients, which means they can't passively accept topics from the network.
HTTP is a 1 to 1 protocol. The client sends an HTTP request, and the server answers. In IoT applications, devices broadcast messages to each other. The HTTP network makes it complex and expensive.
Heavy Weight Protocol: HTTP with many headers and rules, not suitable for constrained networks.
Most high-performance scalable systems use an asynchronous messaging network rather than web services. MQTT is especially suited to address the demands of industrial control systems due to its low overhead, publish/subscribe model, and bidirectional capabilities.