Bevy Client Server Events

Simple event-based client-server networking library for Bevy.

Easily send bevy events to/from a client/server without worrying about serialization or network transport details.

Builds off of the renet/bevy_renet library and attempts to simplify the configuration and management of types to be sent through a network.

Goals:

• Simplified network setup and configuration
• Easily send any types to/from a client/server

Requirements:

• serde to derive Serialize and Deserialize on your types

Events

The following events are useful for servers:

• EventWriter<StartServer> - Send this event to start a server
• EventWriter<StopServer> - Send this event to stop a running server
• EventReader<ClientConnected> - Received whenever a new client is connected
• EventReader<ClientDisconnected> - Received whenever a client has disconnected
• EventReader<ReceiveFromClient<T>> - Received whenever a client has sent type T to the server
• EventWriter<SendToClient<T>> - Send this event to have a particular client receive type T
• EventWriter<SendToClients<T>> - Send this event to have all connected clients receive type T

The following events are useful for clients:

• EventWriter<ConnectToServer> - Send this event to connect to a server
• EventWriter<DisconnectFromServer> - Send this event to disconnect from the server
• EventWriter<SendToServer<T>> - Send this event to have the server receive type T
• EventReader<ReceiveFromServer<T>> - Received whenever the server has sent type T to the client

Both the client and the server can receive the EventReader<NetcodeTransportError> events to deal with networking errors.

Examples

There are a few examples in the examples/ directory.

Ping

See the examples/ping.rs file for a simple ping-pong example.

In one terminal session, start the server: cargo run --example ping -- -s

In another terminal session, connect with a client: cargo run --example ping

With the client window in focus, hit ENTER to send a Ping. The server will respond with a Pong.

In this example, we want to send a Ping event to the server and receive a Pong event in return.

#[derive(Event, Serialize, Deserialize)]
pub struct Ping;

#[derive(Event, Serialize, Deserialize)]
pub struct Pong;

When setting up our App, we need to pass it to the client_server_events_plugin macro and provide all the types to be sent over the network.

fn main() {
    // ...
    let mut app = App::new();
    client_server_events_plugin!(
        app,
        Ping => NetworkConfig::default(),
        Pong => NetworkConfig::default()
    );
    // ...

You can provide type-specific network configuration, such as reliability, resend time, max memory usage, etc.

The macro should be run regardless of whether this instance will be a server or a client.

You can choose to start a server instance or connect to a server as a client using events.

fn start_server(mut start_server: EventWriter<StartServer>) {
    start_server.send(StartServer::default()); // Binds to 127.0.0.1:5000 with no encryption by default.
}

fn connect_as_client(mut connect_to_server: EventWriter<ConnectToServer>) {
    connect_to_server.send(ConnectToServer::default()); // Connects to 127.0.0.1:5000 with no encryption by default.
}

Then you can send/receive events as desired.

fn update_client(
    mut send_ping: EventWriter<SendToServer<Ping>>,
    mut receive_pong: EventReader<ReceiveFromServer<Pong>>,
) {
    // ...
    send_ping.send(SendToServer { content: Ping });
    // ...
    for ReceiveFromServer { content } in receive_pong.iter() {
        // Do something with content (Pong).
        // ...
    }
}

fn update_server(
    mut receive_ping: EventReader<ReceiveFromClient<Ping>>,
    mut send_pong: EventWriter<SendToClient<Pong>>,
) {
    for ReceiveFromClient { client_id, content } in receive_ping.iter() {
        // Do something with content (Ping).
        send_pong.send(SendToClient {
            client_id,
            content: Pong,
        });
    }
}

Features Example

See the examples/features.rs file for examples of more features, such as encryption, broadcasting, networking error handling, and client connect/disconnect events.

In one terminal session, start the server: cargo run --example features -- -s

In another terminal session, connect with a client: cargo run --example features

The server and client will use encryption to communicate.

Every 500 frames the server will broadcast a message of it's frame count.

With focus on the server window:

• Hit ESC to stop the server
• Hit ENTER to start the server

With focus on the client window:

• Hit ESC to disconnect from the server
• Hit ENTER to reconnect to the server
• Hit SPACE to send a message of type PlayerMovement

The server will respond to the PlayerMovement message with a ServerResponse message.

Other Networking Crates

This crate was created because I wanted the quickest and easiest way to send types through a network.

Other solutions seem to have me bogged down in transport/networking/channel details.

This crate is ideal for prototyping and small client-server games.

An alternative with more bells & whistles would be bevy_replicon.

A mature alternative with more customizability would be bevy_renet.

Bevy Compatibility