MQTT

MQTT is a lightweight publish/subscribe messaging protocol. Clients publish messages to named topics on a broker, and the broker forwards each message to every client subscribed to a matching topic. Sparkplug B is a specification layered on top of MQTT for industrial payloads.

Source checked12/12 values · 2026-10-25

Specification

2 sources

Transports	tcp, websocket
Architecture	publish subscribe
Encoding	binary
Standard body	OASIS
Standard ref	MQTT Version 5.0

Default ports

IANA assignments

1883TCPMQTT

8883TCPMQTT over TLS

Study notes

Quality of Service levels: 0 delivers at most once, 1 at least once, 2 exactly once.
Topic filters use + for one level and # for all remaining levels.

Safety

Port 1883 is unencrypted. Use TLS on port 8883 and require client authentication on any broker reachable from outside the plant network.