# rumqttc

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A pure rust MQTT client which strives to be robust, efficient and easy to use. This library is backed by an async(using tokio) eventloop which enables users to send and receive MQTT messages in correspondence with a broker.

## Examples

A simple synchronous publish and subscribe
----------------------------

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

let mut mqttoptions = MqttOptions::new("rumqtt-sync", "test.mosquitto.org", 1883);
mqttoptions.set_keep_alive(Duration::from_secs(5));

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();
   thread::sleep(Duration::from_millis(100));
});

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

A simple asynchronous publish and subscribe
------------------------------

```rust
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);
mqttoptions.set_keep_alive(Duration::from_secs(5));

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();
        time::sleep(Duration::from_millis(100)).await;
    }
});

while let Ok(notification) = eventloop.poll().await {
    println!("Received = {:?}", notification);
}
```

Quick overview of features
- Eventloop orchestrates outgoing/incoming packets concurrently and handles 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
- Support for WebSockets
- Secure transport using TLS

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.