Robust, ergonomic CoAP server in Rust

An asynchronous CoAP server with a modern and ergonomic API for larger scale applications, inspired by warp and actix. CoAP offers an excellent alternative to HTTP for resource constrained environments like IoT devices.

• Ergonomic: Fluent app-builder API makes it easy to compose rich applications, including those that use more advanced CoAP features.
• Concurrent: High concurrency is supported by using a separate spawned task for each request, allowing long running requests to not interfere with shorter running ones at scale.
• Feature-rich: Conveniently supports a wide range of CoAP server features including Observe, and Block-wise Transfer.
• Flexible: Supports pluggable transport backends with goals of supporting alternative async runtimes like embassy.

Example

```rust use coapserver::app::{CoapError, Request, Response}; use coapserver::{app, CoapServer, FatalServerError, UdpTransport};

[tokio::main]

async fn main() -> Result<(), FatalServerError> { let server = CoapServer::bind(UdpTransport::new("0.0.0.0:5683")).await?; server.serve( app::new().resource( app::resource("/hello").get(handlegethello)) ).await }

async fn handlegethello(request: Request) -> Result { let whom = request .unmatchedpath .first() .cloned() .unwraporelse(|| "world".tostring());

let mut response = request.new_response();
response.message.payload = format!("Hello, {whom}").into_bytes();
Ok(response)

} ```

To experiment, I recommend using the excellent coap-client command-line tool, as with:

$ coap-client -m get coap://localhost/hello Hello, world

See examples for more.

Features

This project aims to be a robust and complete CoAP server, and in particular a more convenient alternative to MQTT for Rust-based projects:

• [x] Correct and convenient Observe support (RFC 7641)
• [x] Block-wise transfer support (RFC 7959)
• [x] Resource discovery and filtering via /.well-known/core (RFC 6690)
• [x] Multicast UDP
• [x] Fully concurrent request handling (no head-of-line blocking or scaling surprises!)
• [x] Ping/Pong keep-alive messages

Desired but not implemented:

• [ ] [Non-piggybacked responses](https://github.com/jasta/coap-server-rs/issues/4)
• [ ] Secure transports (OSCORE and DTLS)

Related Projects

• martindisch/coap-lite: used by this project as the low-level basis for CoAP protocol support
• Covertness/coap-rs: original server I used but outgrew when I needed more robust features like generic Observe support and /.well-known/core filtering.
• ryankurte/rust-coap-client: inspired the creation of this crate based on the excellent generalization of client backends
• google/rust-async-coap