Initial love with mqtt

Before ： After work this afternoon, I ate noodles with my back-end colleagues in the noodle shop downstairs , While waiting for a meal , The ordering machine keeps reporting ：“ You have a new take out order , Please handle in time ！”, Asked the back-end colleague ​：“ Do you know how this real-time voice broadcast is realized ？”, I don't know ​！ Ha ha ha ​！！！ Because we are engaged in Internet development , Strictly speaking , This belongs to the category of the Internet of things ​！ Later, after playing games with friends from the Internet of things, she learned that it was through MQTT Implementation of message queuing transmission protocol ！ Because she has done the function of one button alarm system ！​ In fact! ​！ The Internet has encountered similar functions in its usual development , In fact, it calls and publishes as usual / subscribe api The same thing ​！！！ So let's learn about the agreement today ​！！！​

MQTT It's a client based - Server news release / Subscription transport protocol .MQTT The agreement is light weight 、 Simple 、 Open and easy to implement , These features make it very versatile . In many cases , Including in a limited environment , Such as ： Machines and machines （M2M） Communications and the Internet of things （IoT）. Its presence , Communication of sensors via satellite link 、 Occasionally dialing medical devices 、 Smart home 、 And some miniaturized equipments have been widely used .

1、 The message broker Broker：

Common information proxy platforms ：

1.mosquitto：【 brief introduction 】mosquitto yes ecpllse The open source Broker,

2.EMQ：【 brief introduction 】EMQ It is an open-source product made by Chinese people Broker,

3.HiveMQ：【 brief introduction 】HiveMQ It's enterprise class Broker,

4.MqttWk：【 brief introduction 】mosquitto It is written by Alibaba based on nutzboot+nrtty+redis+kafka Realized MQTT Open source services Broker,

The three functions of information agency ：

​1. Receive messages from the device ,

2. Filtering messages ,

3. Send a message to the device subscribing to the theme change ,

2、 Publish and subscribe mode ：

Subscription contains topic filter （Topic Filter） And maximum quality of service （QoS）. The subscription will have a conversation with （Session） relation . A session can contain multiple subscriptions . Each subscription in each session has a different topic filter .

After each client establishes a connection with the server, it is a session , There is state interaction between the client and the server . A conversation exists between networks , It is also possible to span multiple continuous network connections between the client and the server .​

3、 The theme ：

Tag to connect to an application message , This tag matches the subscription of the server . The server will send the message to each client of the tag that the subscription matches .

A wildcard filter for topic names , In order

4、 Service quality level ：