MQTT protocol | Specification | Clarifications

Here i share some important stuff about MQTT protocol from MQTT wiki. MQTT is widely used and most popular protocol. We already discuss MQTT protocol in this article : MQTT Protocol | MQTT in Depth | MQTT vs CoAP

Recommended :

• https://iotbyhvm.ooo/iot-data-protocols/
• CoAP Protocol- Constrained Application Protocol

MQTT protocol | Specification | Clarifications

MQTT used to stand for MQ Telemetry Transport, but is today referred to simply as MQTT and is no longer an acronym. It is an extremely simple and lightweight Publish/Subscribe messaging protocol invented at IBM and Arcom (now Eurotech) to connect restricted devices in low bandwidth, high-latency or unreliable networks. MQTT was originally designed to connect sensor nodes over communication networks that are unreliable or high-latency, or both.

MQTT Protocol Specification

The current formal MQTT protocol specification can be found at:

• MQTT v3.1.1 specification

The current MQTT-SN specification from IBM can be found at:

• MQTT-SN v1.2 specification

Clarifications

As questions arise around particular aspects of the specification, we are collecting clarifications:

• Topic Format
• Security considerations
• Are topics dynamic?
• Overlapping topics
• KeepAlive for the client
• Miscellaneous clarifications
• MQTT over Websockets
• Duplicates on QOS 0
• Clarify UTF8 strings
• Will Message UTF8 Support
• ClientID autogeneration

Ideas for future enhancement

Ideas (and reasons for why they may be required) are being collected here:

• ClientID autogeneration
• Topic string enhancement
• Broker auto-discovery
• URL scheme
• Status field for acks
• Add messageid to ping
• Will Message UTF8 Support
• Bridge protocol
• Extended CONNACK codes
• Registered topics like MQTT-SN
• MQTT for Centralised Data Collection
• Time To Live for retained message

Items fixed in the updated OASIS spec

• Extended ClientID
• Short usernames and passwords

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