Enum Version

pub enum Version {
    Undetermined = 0,
    V3_1_1 = 4,
    V5_0 = 5,
}

MIT License

Copyright (c) 2025 Takatoshi Kondo

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. MQTT protocol version enumeration

Represents the supported MQTT protocol versions. Each variant corresponds to the protocol level value as defined in the MQTT specification. This is used throughout the library to handle version-specific behavior and feature availability.

Protocol Level Values

The numeric values correspond to the Protocol Level field in the CONNECT packet:

• v3.1.1 uses protocol level 4
• v5.0 uses protocol level 5
• Undetermined is used by servers to accept any supported version

Examples

use mqtt_protocol_core::mqtt::version::Version;

// Client specifies a specific version
let client_version = Version::V5_0;

// Server accepts any supported version
let server_version = Version::Undetermined;

match server_version {
    Version::V3_1_1 => println!("Using MQTT v3.1.1"),
    Version::V5_0 => println!("Using MQTT v5.0"),
    Version::Undetermined => println!("Waiting for client CONNECT to determine version"),
}

Variants

Undetermined = 0

Version to be determined by incoming CONNECT packet

Used by MQTT servers to indicate that the protocol version should be determined based on the protocol level in the incoming CONNECT packet from the client. The server will accept either v3.1.1 or v5.0 connections and adapt accordingly. Not a valid protocol level value itself.

V3_1_1 = 4

MQTT version 3.1.1 (protocol level 4)

The widely adopted MQTT v3.1.1 specification. This version provides the core MQTT functionality including QoS levels, retained messages, last will and testament, and persistent sessions.

V5_0 = 5

MQTT version 5.0 (protocol level 5)

The latest MQTT specification with enhanced features including:

• User properties and reason codes
• Topic aliases and subscription identifiers
• Message expiry and session expiry intervals
• Enhanced authentication (AUTH packets)
• Improved error handling and flow control

Trait Implementations

impl Clone for Version

fn clone(&self) -> Version

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Version

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for Version

fn eq(&self, other: &Version) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for Version

impl StructuralPartialEq for Version