mqtt5-protocol

MQTT v5.0 and v3.1.1 protocol implementation - packets, encoding, and validation.

Features

• no_std compatible - Works on embedded systems without heap or standard library
• Platform-agnostic - Runs on Linux, macOS, Windows, WASM, and bare-metal embedded targets
• Zero-copy parsing - Uses bytes crate for efficient buffer management
• Full MQTT v5.0 - All packet types, properties, and reason codes

Installation

[dependencies]
mqtt5-protocol = "0.8"

For Embedded (no_std)

[dependencies]
mqtt5-protocol = { version = "0.8", default-features = false }

For Single-Core Embedded

[dependencies]
mqtt5-protocol = { version = "0.8", default-features = false, features = ["embedded-single-core"] }

Supported Targets

Usage

Standard (std)

use mqtt5_protocol::packet::connect::ConnectPacket;
use mqtt5_protocol::packet::MqttPacket;
use mqtt5_protocol::types::ConnectOptions;
use bytes::BytesMut;

let options = ConnectOptions::new("client-id");
let connect = ConnectPacket::new(options);

let mut buf = BytesMut::new();
connect.encode(&mut buf)?;

Embedded (no_std)

#![no_std]
extern crate alloc;

use mqtt5_protocol::packet::connect::ConnectPacket;
use mqtt5_protocol::packet::MqttPacket;
use mqtt5_protocol::types::ConnectOptions;
use mqtt5_protocol::time::{set_time_source, update_monotonic_time};
use bytes::BytesMut;

fn init_mqtt() {
    set_time_source(0, 0);
}

fn timer_tick(millis_since_boot: u64) {
    update_monotonic_time(millis_since_boot);
}

fn create_connect_packet() {
    let options = ConnectOptions::new("device-001");
    let connect = ConnectPacket::new(options);

    let mut buf = BytesMut::with_capacity(128);
    connect.encode(&mut buf).unwrap();
}

Embedded Time Provider

On no_std targets, time functions (Instant::now(), SystemTime::now()) require external time sources since there's no OS. The library provides a time provider mechanism:

use mqtt5_protocol::time::{
    set_time_source,      // Initialize both monotonic and epoch time
    update_monotonic_time, // Update monotonic clock (for Instant)
    update_epoch_time,     // Update wall clock (for SystemTime)
    Instant,
    Duration,
};

// Call from your timer interrupt or main loop
fn update_time(millis_since_boot: u64) {
    update_monotonic_time(millis_since_boot);
}

// Now Instant::now() and elapsed() work correctly
let start = Instant::now();
// ... do work ...
let elapsed = start.elapsed();

Time Provider Functions

Implementation Notes

• Uses AtomicU32 pairs for 32-bit target compatibility
• Thread-safe with SeqCst ordering
• Returns 0/epoch if time source not initialized

Crate Organization

This crate provides the protocol layer used by:

• mqtt5 - Native client and broker for Linux, macOS, Windows
• mqtt5-wasm - WebAssembly client and broker for browsers

Module Structure

Features

License

Licensed under either of Apache License, Version 2.0 or MIT license at your option.