simple_json_server

This library is intended to make it very easy to build a JSON-based server. Because its JSON it is easily called from multiple languages (think a TypeScript client). The goal is to provide a lot of functionality out of the box but with excellent ergonomics so that simple servers are easily built without almost any boilerplate.

This library is intended to make it very easy to build a JSON-based server. Because its JSON it is easily called from multiple languages (think a TypeScript client). The goal is to provide a lot of functionality out of the box but with excellent ergonomics so that simple servers are easily built without almost any boilerplate.

The macro both creates your simple server (an actor) from an impl of your struct and also generates documentation for your actor so its 100% clear how to call it.

The way simple_json_server works is:

1. Create a struct and create an impl block for it. The impl block should contain all the methods you want to expose on your server. The methods must be pub async fn and take &self as the first parameter. Others are ignored for this purpose.

2. The #[actor] macro will generate the code to make your struct into an actor. Each method in turn gets turned into a JSON-RPC where:

   • The RPC name is the name of the method in your impl
   • The parameters are serialized as JSON parameters of the method. They are automatically turned into a JSON object with the name of the parameter as the key. The value is the JSON equivalent of the value of the parameter
   • The return value is the JSON-serialized return value of the method
   • The macro will generate documentation for your actor so it's 100% clear how to call it including the specific JSON payload needed to call the method

3. The create method will start a server for you and begin listening for incoming JSON-RPC calls via HTTP. create_ws will do the same but via WebSocket. Options for https and wss are also provided.

Quick Start

The easiest way to create an actor is using the #[actor] macro:

use simple_json_server::{Actor, actor};

#[derive(Debug, Clone)]
struct Calculator {
    memory: f64,
}

impl Calculator {
    fn new() -> Self {
        Self { memory: 0.0 }
    }
}

#[actor]
impl Calculator {
    pub async fn add(&self, a: f64, b: f64) -> f64 {
        a + b
    }

    pub async fn subtract(&self, a: f64, b: f64) -> f64 {
        a - b
    }

    pub async fn get_memory(&self) -> f64 {
        self.memory
    }
}

fn main() {
    let calc = Calculator::new();

    calc.create(8080);
}

The #[actor] Macro

The #[actor] procedural macro automatically implements the Actor trait for your struct by:

1. Analyzing public async methods in the impl block
2. Generating message structs for each method's parameters
3. Creating a dispatch method that handles JSON messages mapped from the method parameters.

Features

• Automatic JSON serialization/deserialization of parameters and return values
• Snake_case to PascalCase conversion for message struct names
• Comprehensive RustDoc generation with method tables, JSON payload examples, and usage instructions
• TLS/SSL support for secure HTTPS and WSS (WebSocket Secure) connections

Method Requirements

The macro only processes methods that are:

• Public (pub)
• Async (async fn)

Private methods and synchronous methods are ignored.

Server Support

The library includes built-in HTTP and WebSocket server support. Use the create_options method to start a server.

Note: create and variants on create consumes the actor (moves it), preventing accidental use after starting the server. This is a safety feature that ensures the actor is only used within the server context.

use simple_json_server::{Actor, actor};

#[derive(Debug, Clone)]
struct MyActor {
    name: String,
}

#[actor]
impl MyActor {
    pub async fn greet(&self, name: String) -> String {
        format!("Hello, {}! I'm {}", name, self.name)
    }
}

fn main() {
    // Create separate actor instances since create_options consumes the actor
    let http_actor = MyActor { name: "HTTP-Server".to_string() };
    let ws_actor = MyActor { name: "WebSocket-Server".to_string() };

    // Start HTTP server on port 8080 (consumes http_actor)
    http_actor.create(8080);

    // Start WebSocket server on port 8081 (consumes ws_actor)
    ws_actor.create_ws(8081);

    // Keep main thread alive
    loop {
        std::thread::sleep(std::time::Duration::from_secs(1));
    }
}

HTTP Server

The HTTP server expects POST requests with the method name in the URL path and parameters in the JSON body:

# Call the 'greet' method
curl -X POST http://127.0.0.1:8080/greet -d '{"name": "World"}'

WebSocket Server

The WebSocket server expects JSON messages in the standard format:

{"method": "greet", "params": {"name": "World"}}

TLS/SSL Support

The library supports secure connections using TLS for both HTTP (HTTPS) and WebSocket (WSS) protocols.

Setting up TLS

First, create a TlsConfig with your certificate and private key files:

use simple_json_server::{Actor, actor, TlsConfig};

let tls_config = TlsConfig::new("cert.pem", "key.pem");

HTTPS Server

// Start an HTTPS server
actor.create_https(8443, tls_config);

WSS (WebSocket Secure) Server

// Start a WSS server
actor.create_wss(8444, tls_config);

Generating Test Certificates

For development and testing, you can generate self-signed certificates:

# Use the provided script
./generate_cert.sh

# Or manually with OpenSSL
openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -days 365 -nodes

Testing HTTPS Endpoints

# Use -k flag to accept self-signed certificates
curl -k -X POST https://127.0.0.1:8443/greet -d '{"name": "World"}'

TLS Configuration

The TlsConfig struct supports:

• Certificate file: PEM format certificate file
• Private key file: PEM format private key file (PKCS#8)
• Automatic loading: Certificates are loaded asynchronously when the server starts

Examples

There are examples in the simple_json_server crate itself. See the examples/ directory for a more complete (yet simple) demo. The demo will build on its own.

cd simple_json_server/examples 
# Basic calculator example
cargo run --example calculator

# HTTP and WebSocket server example
cargo run --example server

# TLS/SSL server example (HTTPS and WSS)
cargo run --example tls_server

# The full example
cd ../../examples/demo
cargo run

Actor Trait

The Actor trait defines two methods:

pub trait Actor {
    /// Process a method call with parameters
    fn dispatch(&self, method_name: &str, msg: &str) -> String;

    /// Start a server (HTTP or WebSocket) on the specified port
    /// This method consumes the actor, preventing further use after starting the server
    fn create_options(self, port: u16, websocket: bool)
    where
        Self: Send + Sync + Sized + 'static;
}

If you need more control, you can implement the Actor trait manually instead of using the #[actor] macro.

Documentation

The #[actor] macro automatically generates comprehensive RustDoc documentation for your Actor implementations. To view the generated documentation:

cargo doc --open

The generated documentation includes:

• Method overview table with parameters and return types
• Detailed method documentation extracted from your doc comments
• JSON payload examples for each method
• Usage examples showing how to call each method via dispatch
• Parameter specifications with type information

This makes it easy to understand the JSON API without looking at the source code!