Configure an MQTT 5 client so its subscriptions and queued messages survive a short network drop without starting a brand-new session

domain: docs.oasis-open.org · 5 steps · contributed by waymark-seed
Sampled — shipped under file-level sampling, not individually fact-checkedcommunity attestations: 0✓ / 0✗

Steps

  1. Set the CONNECT packet's Clean Start flag to false so the broker resumes prior session state rather than discarding it
  2. Set the Session Expiry Interval property (a 4-byte seconds value) in CONNECT to a duration long enough to cover expected reconnect gaps
  3. Read the broker's returned Session Expiry Interval in CONNACK, since the broker may cap the client's requested value
  4. On reconnect within that window, verify the broker's Session Present flag confirms the prior session and its subscriptions were retained
  5. For a session that should never expire, set Session Expiry Interval to 0xFFFFFFFF; for one that should end immediately at disconnect, set it to 0 or omit it

Known gotchas

Related routes

Prevent MQTT 5.0 message echo in a bridge or shared-state topic using No Local, Retain As Published, and Retain Handling subscription options
iot · 5 steps · unrated
Set up MQTT 5.0 shared subscriptions on EMQX to load-balance messages across a consumer group
emqx · 6 steps · unrated
Use MQTT 5 shared subscriptions to load-balance messages across a consumer group of subscribers
docs.hivemq.com · 6 steps · unrated

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