Overview

"This library stinks!" ... "Unless you like durian"

durian is a client-server networking library built on top of the QUIC protocol which is implemented in Rust by quinn.

It provides a thin abstraction layer above the lower-level details of connection management, byte management, framing, and more, to make writing netcode easier and allow the user to focus on the messaging contents instead. Serialization and deserialization are built into the APIs so you can send and receive exact Packets as structs for ease of development.

durian is a general purpose library, but was made primarily for me to dabble in game development. It has been tested and working with the Bevy game engine.

Full documentation can be found at https://docs.rs/durian/latest/durian/

Crates.io: https://crates.io/crates/durian/

Disclaimer

This library is in very early (but very active!) development, meaning a LOT of it will change rapidly.
In its current state, it's usable to create a quick multiplayer demo. I use it myself to learn game development.

This is not production ready, and is missing a lot of features to make it production ready (see Features list below).

However, if you are trying to build something and want to avoid a lot of the headache of lower-level netcode details, and don't need the "production" features, such as a multiplayer game demo, LAN sandbox applications, etc., then feel free to try it out!

durian's goal is to make it as simple as possible to setup netcode (See the examples below).

Features

• Simultaneous basic Client/Server connection management and operations
• Both async and sync APIs for different caller contexts
• Multiplexing without head of line blocking (QUIC feature)
  • Dedicated stream for each Packet type and multi-threaded
• Reliable packets: guaranteed delivery of all messages
• Ordered packets: packets are received in the same order they are sent on each stream
• Packet Fragmentation and re-assembly automatically for you
• Macros to ease creation of Packets and registration
• Send and receive packets simultaneously
• Various Client/Server configurations
  • keep-alive-intervals
  • idle-timeout
  • ALPN Protocol

Not yet done

• Certificate authentication between client-server
• More complex connection configurations such as:
  • Pluggable cryptography
• Handshake protocol
• Connection/streams re-establishment
• Reusing an Endpoint across multiple PacketManagers (for client connected to multiple servers, or having different Packet contracts)
• Better Error handling/messaging
• Unreliable packets
• Unordered packets
• Probably lots more

Cargo.toml Dependency

Add durian to your Cargo.toml via cargo add durian or manually:

[dependencies]
durian = "0.3"

Packet/PacketBuilder

There are 2 steps needed to create a Packet to be used with durian:

1. durian allows for structuring Packets as simple structs. The structs must implement Trait Packet, which has a single function Packet::as_bytes() which will be called for serializing the Packet into bytes to be sent over the wire between client and server.

2. There also needs to be a struct that implements PacketBuilder which is used to deserialize from bytes back into your Packet struct via the PacketBuilder::read() function.

For your convenience, durian is bundled with durian_macros which contains a few macros that help autogenerate Impl blocks for a struct for both Packet and PacketBuilder. The only requirement is the struct must be de/serializable, meaning all nested fields also need to be de/serializable.

#[bincode_packet] will de/serialize your Packet using bincode and applies necessary derive macros automatically for you.

use durian::bincode_packet;

// Automatically implements Packet, and generates a PositionPacketBuilder that implements 
// PacketBuilder.  You can also add other macros such as derive macros so long as they don't
// conflict with what #[bincode_packet] adds (See bincode_packet documentation).
#[bincode_packet]
#[derive(Debug)]
struct Position {
    x: i32,
    y: i32
}

// Works for Unit (empty) structs as well
#[bincode_packet]
struct Ack;

You can also use the derive macros (BinPacket and UnitPacket) manually:

use durian::serde::{Deserialize, Serialize};
use durian::{BinPacket, UnitPacket};

#[derive(Serialize, Deserialize, BinPacket)]
#[serde(crate = "durian::serde")]
struct Position { x: i32, y: i32 }

#[derive(UnitPacket)]
struct Ack;

PacketManager

PacketManager is what you will use to initiate connections between clients/servers, and send/receive Packets.

A PacketManager would be created on each client to connect to a single server, and one created on the server to connect to multiple clients. It contains both synchronous and asynchronous APIs, so you can call the functions both from a synchronous context, or within an async runtime (Note: the synchronous path will create a separate isolated async runtime context per PacketManager instance.)

There are 4 basic steps to using the PacketManager, which would be done on both the client and server side:

1. Create a PacketManager via new() or, if calling from an async context, new_for_async()

2. Register the Packets and PacketBuilders that the PacketManager will receive and send using register_receive_packet() and register_send_packet().
   The ordering of Packet registration matters for the receive channel and send channel each - the client and server must register the same packets in the same order, for the opposite channels.

   • In other words, the client must register receive packets in the same order the server registers the same as send packets, and vice versa, the client must register send packets in the same order the server registers the same as receive packets. This helps to ensure the client and servers are in sync on what Packets to send/receive, almost like ensuring they are on the same "version" so to speak, and is used to properly identify Packets.
   • For your convenience, durian_macros comes bundled with 2 macros that simplify registration of send and receive packets: register_receive!(), and register_send!()

3. Initiate connection(s) with init_client() (or the async variant async_init_client() if on the client side, else use init_server() (or the async variant async_init_server) if on the server side.

4. Send packets using any of broadcast(), send(), send_to() or the respective async variants if calling from an async context already. Receive packets using any of received_all() , received(), or the respective async variants.

Putting these together:

use durian::{ClientConfig, PacketManager, bincode_packet, register_receive, register_send};

#[bincode_packet]
struct Position { x: i32, y: i32 }
#[bincode_packet]
struct ServerAck;
#[bincode_packet]
struct ClientAck;
#[bincode_packet]
struct InputMovement { direction: String }

fn packet_manager_example() {
    // Create PacketManager
    let mut manager = PacketManager::new();

    // Register send and receive packets
    // Using macros
    let register_results = register_receive!(
        manager, 
        (Position, PositionPacketBuilder), 
        (ServerAck, ServerAckPacketBuilder)
    );
    let send_results = register_send!(manager, ClientAck, InputMovement);
    // Validate registrations succeeded
    assert!(receive_results.iter().all(|r| r.is_ok()));
    assert!(send_results.iter().all(|r| r.is_ok()));

    // Or equivalently with manual registrations:
    // manager.register_receive_packet::<Position>(PositionPacketBuilder).unwrap();
    // manager.register_receive_packet::<ServerAck>(ServerAckPacketBuilder).unwrap();
    // manager.register_send_packet::<ClientAck>().unwrap();
    // manager.register_send_packet::<InputMovement>().unwrap();

    // Initialize a client
    let client_config = ClientConfig::new("127.0.0.1:5001", "127.0.0.1:5000", 2, 2);
    manager.init_client(client_config).unwrap();

    // Send and receive packets
    manager.broadcast(InputMovement { direction: "North".to_string() }).unwrap();
    manager.received_all::<Position, PositionPacketBuilder>(false).unwrap();

    // The above PacketManager is for the client.  Server side is similar except the packets
    // are swapped between receive vs send channels:

    // Create PacketManager
    let mut server_manager = PacketManager::new();

    // Register send and receive packets
    let server_register_results = register_receive!(
        server_manager, 
        (ClientAck, ClientAckPacketBuilder), 
        (InputMovement, InputMovementPacketBuilder)
    );
    let server_send_results = register_send!(server_manager, Position, ServerAck);
    // Validate registrations succeeded
    assert!(server_receive_results.iter().all(|r| r.is_ok()));
    assert!(server_send_results.iter().all(|r| r.is_ok()));

    // Initialize a client
    let client_config = ClientConfig::new("127.0.0.1:5001", "127.0.0.1:5000", 2, 2);
    server_manager.init_client(client_config).unwrap();

    // Send and receive packets
    server_manager.broadcast(Position { x: 1, y: 3 }).unwrap();
    server_manager.received_all::<InputMovement, InputMovementPacketBuilder>(false).unwrap();
}

Examples

For beginners, creating packets to be sent between clients/server should be extremely straight-forward and the above examples should cover most of what you'd need. For more complex scenarios, such as serializing/deserializing packets in a custom way, can be done by implementing the various Traits yourself, or through extra configurations in the PacketManager.

For a comprehensive minimal example, see the example crate.

I also use this library myself for simple game development. See the multisnakegame repo.

Debugging

durian uses the log API with debug and trace logs. Enable debug logging to see update logs from durian, and enable trace logging to see packet byte transmissions.