Communication Protocols: From HTTP to MQTT

In a connected world, devices and apps exchange data using protocols. HTTP powers the web with request-response messages, while MQTT offers a lightweight route for many devices to share updates via a central broker. Both have a place, depending on goals like speed, bandwidth, and reliability.

HTTP and REST basics

HTTP is built for request-response. A client asks for a resource, a server returns data and status. Each exchange is stateless, making servers simple and scalable. Headers carry information about type, length, and authentication. The same pattern underpins REST APIs, enabling caching, retries, and clear error handling.

  • Simple to test with tools
  • Strong browser and server support
  • Clear semantics for actions and status

MQTT and the publish-subscribe model

MQTT shifts the flow. Clients connect to a broker, publish messages on topics, and subscribe to topics of interest. The broker buffers or forwards messages, delivering data even if a client was offline briefly. This model suits devices with limited power or flaky networks.

  • Very lightweight protocol
  • Decouples producers and consumers
  • QoS levels 0, 1, or 2 ensure delivery
  • Retained messages keep the last value handy

When to choose HTTP or MQTT

HTTP is great for user actions and page data. MQTT shines in IoT or sensor networks with many devices and sporadic connectivity. In some systems, both work together: HTTP for configuration and dashboards, MQTT for live data streams.

  • Use HTTP for web apps and APIs
  • Use MQTT for device telemetry and remote control
  • You can bridge them with adapters or gateways

Security and reliability

Both can be secure with encryption and proper access control. TLS protects data in transit. Authentication, authorization, and regular updates reduce risk. Design for retries, idempotence, and sensible payloads to avoid overload.

  • TLS everywhere
  • Token or certificate-based auth
  • Small, compact message formats

Key Takeaways

  • HTTP and MQTT meet different needs: web interactions vs device messaging
  • MQTT offers lightweight, reliable publish-subscribe for many devices
  • In modern systems, both protocols often co-exist to cover management and data pipelines