AWS Greengrass
User Guide

Greengrass subscriptions and MQTT

Greengrass devices and AWS Greengrass core devices use the industry-standard, lightweight Message Queue Telemetry Transport (MQTT) protocol to communicate within a local group. In addition, AWS Greengrass groups add a layer of structure and security by modeling the expected interactions between devices through subscriptions.

Subscriptions describe a single-direction path of messages inside a group. MQTT messages are sent by a source to a target. The source and target in a subscription can be:

  • An AWS Greengrass device, like a physical sensor, solenoid, switch, or a logical device like a protocol adapter.

  • A Lambda function.

  • Lifecycle-driven events, like a core being restarted.