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# message-io
`message-io` is an event-driven message library to build network applications **easy** and **fast**.
The library manages and processes the socket data streams in order to offer a simple
event message API to the user.
Working as a **generic network manager**, it allows you to implement your own protocol
following some rules, delegating to the library the tedious asynchrony and thread management.
See more [here](#custom-adapter).

<p align="center">
  <img src="https://docs.google.com/drawings/d/e/2PACX-1vSPmycMsWoQq60MPEODcakFQVPkDwVy98AnduTswFNPGBB5dpbIsSCHHBhS2iEuSUtbVaYQb7zgfgjO/pub?w=653&h=305" width="653"/>
</p>

If you find a problem using the library or you have an improvement idea, do not hesitate to open an issue. **Any contribution is welcome!**

## Motivation
Managing sockets is hard because you need to fight with threads, concurrency,
IO errors that come from the OS (which are really difficult to understand in some situations), encoding...
And if you make use of *non-blocking* sockets, it adds a new layer of complexity:
synchronize the events that come asynchronously from the OS poll.

`message-io` offers an easy way to deal with all these mentioned problems,
making them transparently for you,
the programmer that wants to make an application with its own problems.
For that, `message-io` offers a simple API and give only two concepts to understand:
**messages** (the data you send and receive), and **endpoints** (the recipients of that data).
This abstraction also offers the possibility to use the same API independently
of the transport protocol used.
You could change the protocol of your application in literally one line.

## Features
- Asynchronous: internal poll event with non-blocking sockets using [mio](https://github.com/tokio-rs/mio).
- Multiplatform: see [mio platform support](https://github.com/tokio-rs/mio#platforms).
- Multiples transports: **TCP**, **UDP** (with multicast option) and
  **WebSockets** (secure and non-secure option).
- Internal encoding layer: handle messages, not data streams.
- FIFO events with timers and priority.
- Easy, intuitive and consistent API:
  - Follows [KISS principle](https://en.wikipedia.org/wiki/KISS_principle).
  - Abstraction from transport layer: do not think about sockets, think about messages and endpoints.
  - Only two main entities to use:
    - an extensible
    [`Eventqueue`](https://docs.rs/message-io/latest/message_io/events/struct.EventQueue.html)
    to manage all events synchronously,
    - a [`Network`](https://docs.rs/message-io/latest/message_io/network/struct.Network.html)
    to manage all connections (connect, listen, remove, send, receive).
  - Forget concurrence problems: handle thousands of active connections and listeners without any
    effort. "One thread to rule them all".
  - Easy error handling.
    Do not deal with dark internal `std::io::Error` when send/receive from the network.
- High performance:
    - One thread for manage all internal connections over the faster OS poll.
    - Full duplex socket: simultaneous reading/writing operations over same internal OS sockets.

## Getting started
Add to your `Cargo.toml`
```
message-io = "0.9"
```

### Documentation
- [API documentation](https://docs.rs/message-io/)
- [Basic concepts](docs/basic_concepts.md)
- [Examples](examples):
  - [Ping Pong](examples/ping-pong) (a simple client server example)
  - [Multicast](examples/multicast)
  - [Distributed network with discovery server](examples/distributed)
  - [File transfer](examples/file-transfer)

- Applications using `message-io`:
  - [Termchat](https://github.com/lemunozm/termchat): Distributed LAN chat in the terminal.
  - [AsciiArena](https://github.com/lemunozm/asciiarena): Terminal multiplayer deathmatch game.
    (under development, but the communication part using `message-io` is almost complete for reference).

### All in one: TCP, UDP and WebSocket echo server
The following example is the simplest server that reads messages from the clients and respond to them.
It is capable to manage several client connections and listen from 3 differents protocols at the same time.

```rust
use message_io::network::{Network, NetEvent, Transport};

fn main() {
    // Create a Network with an associated event queue for reading its events.
    let (mut network, mut events) = Network::split();

    // Listen for TCP, UDP and WebSocket messages.
    network.listen(Transport::Tcp, "0.0.0.0:3042").unwrap();
    network.listen(Transport::Udp, "0.0.0.0:3043").unwrap();
    network.listen(Transport::Ws, "0.0.0.0:3044").unwrap(); //WebSockets

    loop {
        match events.receive() { // Read the next event or wait until have it.
            NetEvent::Message(endpoint, data) => {
                println!("Received: {}", String::from_utf8_lossy(&data));
                network.send(endpoint, &data);
            },
            NetEvent::Connected(_endpoint) => println!("Client connected"), // Tcp or Ws
            NetEvent::Disconnected(_endpoint) => println!("Client disconnected"), //Tcp or Ws
        }
    }
}
```

### Echo client
The following example shows a client that can connect to the previous server.
It sends a message each second to the server and listen its echo response.
Changing the `Transport::Tcp` to `Udp` or `Ws` will change the underlying transport used.
Also, you can create the number of connections you want at the same time, without any extra thread.

```rust
use message_io::network::{Network, NetEvent, Transport};

enum Event {
    Net(NetEvent),
    Tick,
    // Any other app event here.
}

fn main() {
    // The split_and_map() version allows to combine network events with your application events.
    let (mut network, mut events) = Network::split_and_map(|net_event| Event::Net(net_event));

    // You can change the transport to Udp or Websocket.
    let (server, _ ) = network.connect(Transport::Tcp, "127.0.0.1:3042").unwrap();

    events.sender().send(Event::Tick); // Start sending
    loop {
        match events.receive() {
            Event::Net(net_event) => match net_event { // event from the network
                NetEvent::Message(_endpoint, data) => {
                    println!("Received: {}", String::from_utf8_lossy(&data));
                },
                _ => (),
            }
            Event::Tick => { // computed every second
                network.send(server, "Hello server!".as_bytes());
                events.sender().send_with_timer(Event::Tick, std::time::Duration::from_secs(1));
            }
        }
    }
}
```

## Test it yourself!
Clone the repository and test the *Ping Pong* example
(similar to the *echo* example but more vitaminized).

Run the server:
```
cargo run --example ping-pong server tcp 3456
```
Run the client:
```
cargo run --example ping-pong client tcp 127.0.0.1:3456
```

You can play with it changing the transport, running several clients, disconnect them, etc.
See more [here](examples/ping-pong).

## Do you need a transport protocol that `message-io` doesn't have? Add an adapter! <span id="custom-adapter"><span>

`message-io` offers two *kinds* of APIs.
The **user API**, that talks to `message-io` itself as an user that want to use the library,
and the internal **adapter API** for those who want to add their protocol adapters into the library.

<p align="center">
  <img src="https://docs.google.com/drawings/d/e/2PACX-1vRMwZsL8Tki3Sq9Zc2hpZ8L3bJPuj38zgiMKzBCXsX3wrPnfyG2hp-ijmDFUPqicEQZFeyUFxhcdJMB/pub?w=546&h=276"/>
</p>

If the protocol can be built in top of [`mio`](https://github.com/tokio-rs/mio)
(most of the existing protocol libraries can), then you can add it to `message-io` **really easy**:

1. Add your *adapter* file in `src/adapters/<my-transport-protocol>.rs` that implements the
  traits that you find [here](https://docs.rs/message-io/latest/message_io/adapter/index.html).
  It contains only 7 mandatory functions to implement (see the [template](src/adapters/template.rs)),
  and take little more than 150 lines to implement an adapter file.

1. Add a new field in the `Transport` enum found in [src/transport.rs](src/transport.rs)
  to register your new adapter.

That's all.
You can use your new transport with the `message-io` API like any other.

Oops! one step more, make a *Pull request* so everyone can use it :)

