什麼是 MQTT

MQTT 是物聯網 (IoT) 的 OASIS 標準訊息傳遞協定。

OASIS（Organization Advancement Structured Information Standards / 結構化資訊標準促進組織 ）：全球的非營利組織，主要在發展及整合物聯網、網路服務等領域的相關標準。

References

https://mqtt.org/

MQTT

Summary

MQTT 是設計給 IoT 作為訊息傳遞來使用的協定。通常 IoT 硬件通常會有資源上的限制，所以 MQTT 的特色就是輕量且高效。 下面列出了 MQTT 的特色：

1. Lightweight and Efficient（輕量且高效）
2. Bi-directional Communications（裝置跟服務可雙向溝通）
3. Scale to Millions of Things（可平行擴充）
4. Reliable Message Delivery（可靠的訊息傳遞）
5. Support for Unreliable Networks（適用於網路不穩定的環境之下）
6. Security Enabled （安全性，可使用 TLS 加密訊息）

下圖為 MQTT org 上的 Publish / Subscribe 架構，也繪出一份 flowchart 供紀錄。

MQTT pub/sub Flowchart

flowchart LR
   mc3[MQTT Client
Subscriber: Mobile device] --"Subscribe to topic:temperature"--> mb
   mc2[MQTT Client
Subscriber: Backend device] --"Subscribe to topic:temperature"--> mb
   mb --"Publish: 24°C"--> mc2
   mb --"Publish: 24°C"--> mc3
   subgraph MQtt Broker
     mb[MQTT Broker]
   end

   subgraph MQTT Client
     mc1[Publisher: Temperature Sensor] --"
     Publish to topic: temperature
Publish: 24°C"--> mb
   end

Note

原文 :: mqtt org

MQTT: The Standard for IoT Messaging

MQTT is an OASIS standard messaging protocol for the Internet of Things (IoT). It is designed as an extremely lightweight publish/subscribe messaging transport that is ideal for connecting remote devices with a small code footprint and minimal network bandwidth. MQTT today is used in a wide variety of industries, such as automotive, manufacturing, telecommunications, oil and gas, etc.

Why MQTT?

• Lightweight and Efficient

  MQTT clients are very small, require minimal resources so can be used on small microcontrollers. MQTT message headers are small to optimize network bandwidth.

• Bi-directional Communications

  MQTT allows for messaging between device to cloud and cloud to device. This makes for easy broadcasting messages to groups of things.

• Scale to Millions of Things

  MQTT can scale to connect with millions of IoT devices.

• Reliable Message Delivery

  Reliability of message delivery is important for many IoT use cases. This is why MQTT has 3 defined quality of service levels: 0 - at most once, 1- at least once, 2 - exactly once

• Support for Unreliable Networks

  Many IoT devices connect over unreliable cellular networks. MQTT’s support for persistent sessions reduces the time to reconnect the client with the broker.

• Security Enabled

  MQTT makes it easy to encrypt messages using TLS and authenticate clients using modern authentication protocols, such as OAuth.

MQTT Publish / Subscribe Architecture

MQTT publish subscribe image

Is MQTT a standard?

v5.0 and v3.1.1 are now OASIS standards (v3.1.1 has also been ratified by ISO).