Help Center/ IoT Device Access/ User Guide/ Message Communications/ M2M Communications/ Overview
Updated on 2026-09-30 GMT+08:00
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Overview

Introduction

IoTDA supports MQTT-based machine-to-machine (M2M) communications. The platform processes the connection and communication requests from devices, so you can focus on service implementation. With M2M communications, devices can communicate with each other flexibly.

Figure 1 Service flow
  • During M2M communications, messages sent through the PUB interface and messages received through the SUB interface are counted as charging messages. No additional fee is generated.

Scenarios

  • Instant messaging scenario where a sender and recipient communicate with each other.
  • Smart home scenario where messages are exchanged between mobile apps and smart devices.
  • Device linkage scenario where devices exchange data and communicate with each other.

Constraints

  • Only the standard and enterprise edition instances support the M2M function.
  • Maximum topic length: 128 bytes.
  • Maximum MQTT message size: 1 MB.
  • Maximum subscribers of a topic: 1,000 devices.
  • An MQTT device can subscribe to up to 100 topics (50 custom topics at most).
  • Maximum upstream messages for an MQTT device: 50 messages per second.
Parent topic: M2M Communications