37 lines
1.2 KiB
Markdown
37 lines
1.2 KiB
Markdown
# MQTT Protocol Guide
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## Server or Broker
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A program or device that acts as an intermediary between Clients which publish Application Messages and Clients which have made Subscriptions.
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A Server Accepts Network Connections from Clients.
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Accepts Application Messages published by Clients.
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Processes Subscribe and Unsubscribe requests from Clients.
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Forwards Application Messages that match Client Subscriptions.
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Client ----> Broker(Server) ----> Client
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Publisher ----> Broker -----> Subscriber
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## Subscription and Session
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### Subscription
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A Subscription comprises a Topic Filter and a maximum QoS. A Subscription is associated with a single Session. A Session can contain more than one Subscription. Each Subscription within a session has a different Topic Filter.
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### Session
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A stateful interaction between a Client and a Server. Some Sessions last only as long as the Network
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Connection, others can span multiple consecutive Network Connections between a Client and a Server.
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## Topic Name and Filter
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An expression contained in a Subscription, to indicate an interest in one or more topics. A Topic Filter can include wildcard characters.
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## Packet Identifier
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