Expand description

A pure rust MQTT client which strives to be robust, efficient and easy to use. This library is backed by an async (tokio) eventloop which handles all the robustness and and efficiency parts of MQTT but naturally fits into both sync and async worlds as we’ll see

Let’s jump into examples right away

A simple synchronous publish and subscribe

use rumqttc::{MqttOptions, Client, QoS};
use std::time::Duration;
use std::thread;

let mut mqttoptions = MqttOptions::new("rumqtt-sync", "test.mosquitto.org", 1883);

let (mut client, mut connection) = Client::new(mqttoptions, 10);
client.subscribe("hello/rumqtt", QoS::AtMostOnce).unwrap();
thread::spawn(move || for i in 0..10 {
   client.publish("hello/rumqtt", QoS::AtLeastOnce, false, vec![i; i as usize]).unwrap();

// Iterate to poll the eventloop for connection progress
for (i, notification) in connection.iter().enumerate() {
    println!("Notification = {:?}", notification);

A simple asynchronous publish and subscribe

use rumqttc::{MqttOptions, AsyncClient, QoS};
use tokio::{task, time};
use std::time::Duration;
use std::error::Error;

let mut mqttoptions = MqttOptions::new("rumqtt-async", "test.mosquitto.org", 1883);

let (mut client, mut eventloop) = AsyncClient::new(mqttoptions, 10);
client.subscribe("hello/rumqtt", QoS::AtMostOnce).await.unwrap();

task::spawn(async move {
    for i in 0..10 {
        client.publish("hello/rumqtt", QoS::AtLeastOnce, false, vec![i; i as usize]).await.unwrap();

loop {
    let notification = eventloop.poll().await.unwrap();
    println!("Received = {:?}", notification);

Quick overview of features

  • Eventloop orchestrates outgoing/incoming packets concurrently and hadles the state
  • Pings the broker when necessary and detects client side half open connections as well
  • Throttling of outgoing packets (todo)
  • Queue size based flow control on outgoing packets
  • Automatic reconnections by just continuing the eventloop.poll()/connection.iter() loop`
  • Natural backpressure to client APIs during bad network
  • Immediate cancellation with client.cancel()

In short, everything necessary to maintain a robust connection

Since the eventloop is externally polled (with iter()/poll() in a loop) out side the library and Eventloop is accessible, users can

  • Distribute incoming messages based on topics
  • Stop it when required
  • Access internal state for use cases like graceful shutdown or to modify options before reconnection

Important notes

  • Looping on connection.iter()/eventloop.poll() is necessary to run the event loop and make progress. It yields incoming and outgoing activity notifications which allows customization as you see fit.

  • Blocking inside the connection.iter()/eventloop.poll() loop will block connection progress.


Connecting to a broker using raw ip doesn’t work

You cannot create a TLS connection to a bare IP address with a self-signed certificate. This is a limitation of rustls. One workaround, which only works under *nix/BSD-like systems, is to add an entry to wherever your DNS resolver looks (e.g. /etc/hosts) for the bare IP address and use that name in your code.


pub use mqttbytes::v4::*;
pub use mqttbytes::*;




AsyncClient to communicate with MQTT Eventloop This is cloneable and can be used to asynchronously Publish, Subscribe.

Client to communicate with MQTT eventloop Connection.

Common configuration for (typically) all connections made by a program.

MQTT connection. Maintains all the necessary state

Eventloop with all the state of a connection

Options to configure the behaviour of mqtt connection

State of the mqtt connection.

An error returned from Sender::send().

The sending side of a channel.


Client Error

Critical errors during eventloop polling

Events which can be yielded by the event loop

Key type for TLS authentication

Current outgoing activity on the eventloop

Requests by the client to mqtt event loop. Request are handled one by one.

Errors during state handling

An error returned from Sender::try_send().

Type Definitions