Differences between 3.1.0 and 3.1.1 - mqtt/mqtt.org GitHub Wiki
Differences between versions 3.1.0 and 3.1.1 of the MQTT specification:
3.1.0 specification: http://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html
3.1.1 specification: http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/mqtt-v3.1.1.html
| No. | Description | Reference to 3.1.1 specification |
|---|---|---|
| 1. | Strings must all be verified to be valid UTF-8 | 1.5.3 UTF-8 encoded strings |
| 2. | Must disconnect if string contains NULL | 1.5.3 UTF-8 encoded strings |
| 3. | Protocol name has changed to MQTT | 3.1.2.1 Protocol Name |
| 4. | Protocol level has changed to 0x04 | 3.1.2.2 Protocol Level |
| 5. | ClientIds MAY contain more than 23 encoded bytes | 3.1.3.1 Client Identifier |
| 6. | ClientId MAY be zero bytes long | 3.1.3.1 Client Identifier |
| 7. | ClientId MUST actually be UTF-8 | 3.1.3.1 Client Identifier |
| 8. | ClientId MAY be restricted to alphanumeric chars | 3.1.3.1 Client Identifier |
| 9. | CONNACK has new "session present" flag | 3.2.2.2 Session Present |
| 10. | Ensure that DUP isn't set for QoS 0 | 3.3.1.1 DUP |
| 11. | SUBACK can now indicate failure | 3.9.3 Suback Payload |
| 12. | Clients are allowed to send further Control Packets immediately after sending a CONNECT Packet | 3.1.4 Response |
| 13. | Allow use of WebSocket to initiate connection | 6 Using WebSocket as a network transport |
Other more general changes
- Flags in the fixed header are now specific to the packet type.
- Clarifications to storing/clearing 0 byte retained messages
Terminology changes
- MQ Telemetry Transport is now MQTT
- MQTT Broker is now MQTT Server
- Message ID is now Packet ID
- command message is now Control Packet
- Control Packets "Subscribe" and "Unsubscribe" take Topic Filters, rather than Topic names