MQTT (Message Queuing Telemetry Transport) is a lightweight, publish-subscribe network protocol widely used for messaging in constrained devices and low-bandwidth, high-latency, or unreliable networks. It is particularly popular in Internet of Things (IoT) applications due to its simplicity, small code footprint, and efficient message delivery.

MQTT primarily operates over the TCP/IP protocol. TCP (Transmission Control Protocol) ensures reliable and ordered data transmission, making it well-suited for situations where message loss cannot be tolerated. The use of TCP allows MQTT to guarantee message delivery through its Quality of Service (QoS) levels—QoS 0 (at most once), QoS 1 (at least once), and QoS 2 (exactly once)—depending on the importance of the data being sent.

Though MQTT is designed to run on TCP/IP, it can also work over other protocols such as WebSockets. Using WebSockets allows MQTT messages to be sent from web browsers or other client applications that don’t have direct access to TCP sockets. This makes MQTT flexible for real-time applications that span mobile, web, and embedded platforms.

MQTT’s design philosophy emphasizes low power usage and minimal packet overhead, making it a prime choice for embedded systems and battery-powered devices. The typical MQTT architecture involves clients (sensors, devices, applications) publishing messages to topics via a broker (like Mosquitto, HiveMQ, or EMQX), which then routes these messages to subscribed clients.

Security in MQTT implementations is typically ensured using TLS (Transport Layer Security) over TCP to encrypt data in transit and authenticate connections.

Understanding how MQTT uses TCP/IP and functions efficiently in IoT ecosystems is crucial for professionals looking to develop reliable, scalable IoT solutions. For hands-on expertise and industry-recognized skills, consider enrolling in an IoT certification course.