We're excited to share rtc (https://github.com/webrtc-rs/rtc), a pure Rust WebRTC implementation built on the sans-I/O architecture. With the recent release of rtc v0.7.0, we've achieved feature parity with our async-based webrtc crate while offering complete runtime independence.

## What is Sans-I/O?

Sans-I/O separates protocol logic from I/O operations. Instead of the library performing network reads/writes, YOU control all I/O. The library acts as a pure state machine.

Core API (8 methods):

- poll_write() / poll_event() / poll_read() / poll_timeout() - Get outputs

- handle_read() / handle_timeout() / handle_write() / handle_event() - Feed inputs

## Why Sans-I/O for WebRTC?

WebRTC is a STACK of protocols (ICE, DTLS, SRTP, SCTP, RTP/RTCP). Traditional implementations tightly couple protocol logic with async runtimes, making them runtime-locked, difficult to test without network I/O, and hard to integrate into existing event loops.

Sans-I/O solves this by modeling WebRTC as a composable protocol pipeline where each layer implements the same sansio::Protocol trait.

## Feature Parity

- Full WebRTC 1.0 API (PeerConnection, Media, DataChannel)

- Complete protocol stack (ICE, DTLS, SRTP/SRTCP, SCTP, RTP/RTCP)

- Simulcast with multiple spatial layers

- RTCP Interceptors (NACK, Sender/Receiver Reports, TWCC)

- mDNS support for IP privacy

- W3C and RFC compliant

## Architecture Highlights

- Pure Protocol Pipeline: WebRTC as composable handlers implementing sansio::Protocol. Read: Raw Bytes → Demuxer → ICE → DTLS → SCTP/SRTP → Interceptor → Endpoint. Write path reverses this.

- Zero-Cost Abstractions: Interceptors use generic composition instead of async trait objects. No heap allocations in the hot path.

- Multi-Socket I/O: Handle multiple sockets (mDNS multicast + WebRTC traffic) in one event loop - difficult with async designs.

- Testable: Protocol logic tested without network I/O. Feed synthetic packets, verify state transitions.

## Relationship with async webrtc

rtc (sans-I/O) and webrtc (async) are COMPLEMENTARY:

- Use webrtc for async/await, Tokio integration, quick start

- Use rtc for runtime independence, custom I/O, maximum control, embedded systems

Both actively maintained.

## Recent Milestones

v0.7.0 (Jan 10) - mDNS support for IP privacy with .local hostnames

v0.6.0 (Jan 9) - Complete interceptor framework (NACK, RTCP Reports, TWCC)

v0.5.0 (Jan 5) - Enhanced simulcast support

v0.3.0 (Jan 4) - Initial public release

## Use Cases

Sans-I/O shines for: custom networking, embedded systems, game engines, high performance applications, testing infrastructure, WebAssembly.

## Links

- GitHub: https://github.com/webrtc-rs/rtc

- Crates.io: https://crates.io/crates/rtc (v0.7.0)

- Docs: https://docs.rs/rtc

- Blog: https://webrtc.rs/blog

- Discord: https://discord.gg/4Ju8UHdXMs

Technical deep dives available on our blog exploring the protocol pipeline architecture and interceptor design principles.

We'd love feedback from the Rust and WebRTC communities!