# connect-rs

[![Crates.io][crates-badge]][crates-url]
[![Docs.rs][docs-badge]][docs-url]

[crates-badge]: https://img.shields.io/crates/v/connect.svg
[crates-url]: https://crates.io/crates/connect
[docs-badge]: https://docs.rs/connect/badge.svg
[docs-url]: https://docs.rs/connect

This Rust crate provides a simple, brokerless message-queue abstraction over asynchronous
network streams. It guarantees ordered message delivery and reception, and both TCP and TLS
transports are supported.

## Examples

````rust
// create a client connection to the server
let mut conn = Connection::tcp_client(ip_address).await?;

// construct a new message
let msg = String::from("Hello world!");
let envelope: ConnectDatagram = ConnectDatagram::new(65535, msg.into_bytes())?;

// send a message to the server
conn.writer().send(envelope).await?;

// wait for the echo-server to reply with an echo
if let Some(mut envelope) = conn.reader().next().await {
    // take the message payload from the envelope
    let data: Vec<u8> = envelope.take_data().unwrap();

    // reconstruct the original message
    let msg = String::from_utf8(data)?;
    assert_eq!("Hello world!", msg.as_str());
}
````

In addition to the [crate documentation](https://docs.rs/connect/latest/connect/), please use
the provided [example programs](https://github.com/sachanganesh/connect-rs/tree/main/examples)
as a practical reference for crate usage.

- TCP
    - [TCP Echo Server](https://github.com/sachanganesh/connect-rs/tree/main/examples/tcp-echo-server)
    - [TCP Client](https://github.com/sachanganesh/connect-rs/tree/main/examples/tcp-client)
- TLS (enable `tls` feature flag)
    - [TLS Echo Server](https://github.com/sachanganesh/connect-rs/tree/main/examples/tls-echo-server)
    - [TLS Client](https://github.com/sachanganesh/connect-rs/tree/main/examples/tls-client)

## Why?

When building networked applications, developers shouldn't have to focus on repeatedly solving
the problem of reliable, ordered message delivery over byte-streams. By using a message
queue abstraction, crate users can focus on core application logic and leave the low-level
networking and message-queue guarantees to the abstraction.

Connect provides a `ConnectionWriter` and `ConnectionReader` interface to concurrently send
and receive messages over a network connection. Each user-provided message is prefixed by 8
bytes, containing a size-prefix (4 bytes), version tag (2 bytes), and recipient tag (2 bytes).
The size-prefix and version tag are used internally to deserialize messages received from the
network connection. The recipient tag is intended for crate users to identify the message
recipient, although the library leaves that up to the user's discretion.

Library users must serialize their custom messages into bytes (`Vec<u8>`), prior to
constructing a `ConnectDatagram`, which can then be passed to a `ConnectionWriter`.
Consequently, `ConnectionReader`s will return `ConnectDatagram`s containing the message payload
(`Vec<u8>` again) to the user to deserialize.

Requiring crate users to serialize data before constructing a datagram may appear redundant, but
gives the developer the freedom to use a serialization format of their choosing. This means that
library users can do interesting things such as:

- Use the recipient tag to signify which serialization format was used for that message
- Use the recipient tag to signify the type of message being sent

## Feature Flags

- `tls`: enables usage of tls transport functionality

## Feature Status

| Feature                                             	| Status 	|
|-----------------------------------------------------	|--------	|
| [TCP Client](examples/tcp-client)      	            |    ✓   	|
| [TCP Server](examples/tcp-echo-server) 	            |    ✓   	|
| [TLS Client](examples/tls-client)      	            |    ✓   	|
| [TLS Server](examples/tls-echo-server) 	            |    ✓   	|
| SCTP Client                                         	|        	|
| SCTP Server                                         	|        	|
| DTLS-SCTP Client                                    	|        	|
| DTLS-SCTP Server                                    	|        	|

## Contributing

This crate gladly accepts contributions. Don't hesitate to open issues or PRs.