mqtt_protocol_core/mqtt/
version.rs

1/*!
2 * MIT License
3 *
4 * Copyright (c) 2025 Takatoshi Kondo
5 *
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7 * of this software and associated documentation files (the "Software"), to deal
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24
25/// MQTT protocol version enumeration
26///
27/// Represents the supported MQTT protocol versions. Each variant corresponds
28/// to the protocol level value as defined in the MQTT specification.
29/// This is used throughout the library to handle version-specific behavior
30/// and feature availability.
31///
32/// # Protocol Level Values
33///
34/// The numeric values correspond to the Protocol Level field in the CONNECT packet:
35/// - v3.1.1 uses protocol level 4
36/// - v5.0 uses protocol level 5
37/// - `Undetermined` is used by servers to accept any supported version
38///
39/// # Examples
40///
41/// ```ignore
42/// use mqtt_protocol_core::mqtt::version::Version;
43///
44/// // Client specifies a specific version
45/// let client_version = Version::V5_0;
46///
47/// // Server accepts any supported version
48/// let server_version = Version::Undetermined;
49///
50/// match server_version {
51///     Version::V3_1_1 => println!("Using MQTT v3.1.1"),
52///     Version::V5_0 => println!("Using MQTT v5.0"),
53///     Version::Undetermined => println!("Waiting for client CONNECT to determine version"),
54/// }
55/// ```
56#[derive(PartialEq, Clone, Copy, Debug)]
57pub enum Version {
58    /// Version to be determined by incoming CONNECT packet
59    ///
60    /// Used by MQTT servers to indicate that the protocol version should be
61    /// determined based on the protocol level in the incoming CONNECT packet
62    /// from the client. The server will accept either v3.1.1 or v5.0 connections
63    /// and adapt accordingly. Not a valid protocol level value itself.
64    Undetermined = 0,
65
66    /// MQTT version 3.1.1 (protocol level 4)
67    ///
68    /// The widely adopted MQTT v3.1.1 specification. This version provides
69    /// the core MQTT functionality including QoS levels, retained messages,
70    /// last will and testament, and persistent sessions.
71    V3_1_1 = 4,
72
73    /// MQTT version 5.0 (protocol level 5)
74    ///
75    /// The latest MQTT specification with enhanced features including:
76    /// - User properties and reason codes
77    /// - Topic aliases and subscription identifiers  
78    /// - Message expiry and session expiry intervals
79    /// - Enhanced authentication (AUTH packets)
80    /// - Improved error handling and flow control
81    V5_0 = 5,
82}
mqtt_protocol_core/mqtt/version.rs

mqtt_protocol_core/mqtt/
version.rs
