Mqtt---- bottom (precautions)

Catalog

network connections Network Connections

Theme name and theme filter Topic Names and Topic Filters

Topic wildcards Topic wildcards

Multi level wildcards Multi-level wildcard

  Single layer wildcard

MQTT Support with $ The subject at the beginning Topics beginning with $

Topic names and topic filters are case sensitive .

Tips

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network connections Network Connections

MQTT The protocol requires that the basic transport layer can provide orderly 、 reliable 、 Two way transmission （ From client to server And obedience Service end to client ） The byte stream of . So use tcp/ip agreement

Theme name and theme filter Topic Names and Topic Filters

MQTT Allow topic level separators for topic names and topic filters Topic level separator That is to say ‘/’, Slash （‘/’ U+002F） Used to divide each level of a topic , Provide a hierarchy for topic names .

MQTT Topic wildcards are also allowed Topic wildcards And multiple wildcards Multi-level wildcard And single-layer wildcards

Topic wildcards Topic wildcards

Topic filters for subscriptions can contain special wildcards , Allows you to subscribe to multiple topics at a time . Wildcards can be used in theme filters , But the topic name cannot use wildcards

Multi level wildcards Multi-level wildcard

Digital signs （‘#’ U+0023） It's a wildcard used to match any level of the theme

If he subscribes to such a topic, it will receive a message published with the following topic name ：

 

  Single layer wildcard

plus (‘+’ U+002B) Is a wildcard that can only be used for a single topic level match .

MQTT Support with $ The subject at the beginning Topics beginning with $

The server cannot $ The topic name at the beginning of the character matches the wildcard (# or +) The theme filter at the beginning [MQTT-4.7.2-1]. clothing The service side should prevent the client from using this topic name to exchange messages with other clients .

Topic names and topic filters are case sensitive .

Tips

MQTT The protocol stipulates most of the communication rules , But there are some communication rules that are not stipulated , This part is left to MQTT The server specifies , For example, what are the digits of user name and password , What is the payload format for publishing messages , What is the maximum number of topics subscribed by the client, and so on .