mrpc

A MessagePack-RPC implementation in Rust.

Features

• Write asynchronous RPC servers and clients
• Support for TCP and Unix domain sockets
• Full msgpack-rpc implementation (requests, responses, notifications)
• Support for bidirectional communication - both servers and clients can handle incoming RPC messages
• Built on tokio for async I/O
• Uses rmpv for MessagePack serialization
• Optional serde feature for typed calls and helpers
• Managed server and client shutdown with ServerHandle, Client::shutdown, and Client::close
• Custom asynchronous transports, including in-memory duplex streams
• Structured service, protocol, connection, and disconnect errors
• Early request IDs through RequestHandle for cancellation and other out-of-band protocols

Quick Start

use mrpc::{Client, Connection, Result, RpcSender, Server};
use rmpv::Value;

/// Echo service that returns the method and first parameter.
#[derive(Clone, Default)]
struct Echo;

#[async_trait::async_trait]
impl Connection for Echo {
    async fn handle_request(
        &self,
        _: RpcSender,
        method: &str,
        params: Vec<Value>,
    ) -> Result<Value> {
        Ok(format!("{} -> {}", method, params[0]).into())
    }
}

#[tokio::main]
async fn main() -> Result<()> {
    // Using the default constructor as our ConnectionMaker
    let server = Server::from_fn(Echo::default).tcp("127.0.0.1:0").await?;
    let addr = server.local_addr().unwrap();
    tokio::spawn(server.run());

    // `Connection` is implemented for (), as a convenience for clients who don't need to handle
    // requests or responses.
    let client = Client::connect_tcp(&addr.to_string(), ()).await?;
    let result = client
        .send_request("echo", &[Value::String("Hello there!".into())])
        .await?;
    println!("{}", result);
    Ok(())
}

Serde Feature

Enable the serde feature to unlock typed call/notify APIs and helpers for converting between Rust types and MessagePack values/params.

Typed client-side calls (params and responses):

client.notify("log", &"hello from serde").await?;
let sum: i64 = client.call("add", &(5_i64, 3_i64)).await?;
println!("{sum}");

Typed server-side helpers (decode params and encode responses):

/// Typed handler for a positional-params method.
fn add(params: Vec<Value>) -> Result<Value> {
    let (a, b): (i64, i64) = deserialize_params(params)?;
    serialize_value(&(a + b))
}

/// Typed handler for a single-param notification.
fn log(params: Vec<Value>) -> Result<()> {
    let message: String = deserialize_param(params)?;
    println!("{message}");
    Ok(())
}