mqtt_protocol_core/mqtt/connection/
version.rs

1// MIT License
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3// Copyright (c) 2025 Takatoshi Kondo
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22
23/// MQTT protocol version enumeration
24///
25/// Represents the supported MQTT protocol versions. Each variant corresponds
26/// to the protocol level value as defined in the MQTT specification.
27/// This is used throughout the library to handle version-specific behavior
28/// and feature availability.
29///
30/// # Protocol Level Values
31///
32/// The numeric values correspond to the Protocol Level field in the CONNECT packet:
33/// - v3.1.1 uses protocol level 4
34/// - v5.0 uses protocol level 5
35/// - `Undetermined` is used by servers to accept any supported version
36///
37/// # Examples
38///
39/// ```ignore
40/// use mqtt_protocol_core::mqtt::version::Version;
41///
42/// // Client specifies a specific version
43/// let client_version = Version::V5_0;
44///
45/// // Server accepts any supported version
46/// let server_version = Version::Undetermined;
47///
48/// match server_version {
49///     Version::V3_1_1 => println!("Using MQTT v3.1.1"),
50///     Version::V5_0 => println!("Using MQTT v5.0"),
51///     Version::Undetermined => println!("Waiting for client CONNECT to determine version"),
52/// }
53/// ```
54#[derive(PartialEq, Clone, Copy, Debug)]
55#[cfg_attr(feature = "defmt", derive(defmt::Format))]
56pub enum Version {
57    /// Version to be determined by incoming CONNECT packet
58    ///
59    /// Used by MQTT servers to indicate that the protocol version should be
60    /// determined based on the protocol level in the incoming CONNECT packet
61    /// from the client. The server will accept either v3.1.1 or v5.0 connections
62    /// and adapt accordingly. Not a valid protocol level value itself.
63    Undetermined = 0,
64
65    /// MQTT version 3.1.1 (protocol level 4)
66    ///
67    /// The widely adopted MQTT v3.1.1 specification. This version provides
68    /// the core MQTT functionality including QoS levels, retained messages,
69    /// last will and testament, and persistent sessions.
70    V3_1_1 = 4,
71
72    /// MQTT version 5.0 (protocol level 5)
73    ///
74    /// The latest MQTT specification with enhanced features including:
75    /// - User properties and reason codes
76    /// - Topic aliases and subscription identifiers  
77    /// - Message expiry and session expiry intervals
78    /// - Enhanced authentication (AUTH packets)
79    /// - Improved error handling and flow control
80    V5_0 = 5,
81}
mqtt_protocol_core/mqtt/connection/version.rs

mqtt_protocol_core/mqtt/connection/
version.rs
