MQTT is a lightweight messaging protocol designed for low-bandwidth, high-latency environments, commonly used in machine-to-machine (M2M) communication andInternet of Things (IoT) applications. It was originally developed by IBM in the late 1990s to connect oil pipeline sensors over satellite connections with remote servers.

This protocol operates on a publish-subscribe model, making it highly efficient forIoT device communications which require minimal power and network bandwidth. In this model, devices publish messages to a central server, called a broker, under topic categories. Clients subscribe to these topics to receive updates, ensuring that messages reach all subscribers who need the data without requiring direct connections between senders and receivers.

MQTT is known for its simplicity and ease of implementation. It supports three levels of quality of service for message delivery:

1. At most once (0) – The message is delivered according to the best efforts of the operating environment. Message loss can occur.

2. At least once (1) – The message is assured to arrive but duplicates can occur.

3. Exactly once (2) – The highest quality of service, ensuring that each message is received only once by the intended recipients.

Security in MQTT can be enhanced with SSL/TLS for message encryption, and with username/password authentication at the connection level. This makes MQTT suitable not only for simple sensor messaging but also for more complex scenarios like home automation, industrial IoT, and vehicular communication systems.

Its use of a lightweight broker architecture and efficient data transmission mechanism makes MQTT particularly well-suited for environments where network bandwidth and battery life are limited. This has led to widespread adoption of MQTT in a diverse array of sectors needing reliable, scalable IoT communication.

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