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