WebTransport

WebTransport is a new web API that allows for low-level, bidirectional communication between a client and a server. It's available in the browser as an alternative to HTTP and WebSockets.

WebTransport is layered on top of HTTP/3 which is then layered on top of QUIC. This library hides that detail and tries to expose only the QUIC API, delegating as much as possible to the underlying QUIC implementation.

QUIC provides two primary APIs:

Streams

QUIC streams are ordered, reliable, flow-controlled, and optionally bidirectional. Both endpoints can create and close streams (including an error code) with no overhead. You can think of them as TCP connections, but shared over a single QUIC connection.

Datagrams

QUIC datagrams are unordered, unreliable, and not flow-controlled. Both endpoints can send datagrams below the MTU size (~1.2kb minimum) and they might arrive out of order or not at all. They are basically UDP packets, except they are encrypted and congestion controlled.

Crates

This project is broken up into quite a few different crates:

• web-transport provides a generic interface, delegating to web-transport-quinn or web-transport-wasm depending on the platform.
• web-transport-quinn mirrors the Quinn API, abstracting away the HTTP/3 setup.
• web-transport-noq mirrors the Noq API, a Quinn fork with the same surface area.
• web-transport-wasm wraps the browser API
• web-transport-ws crudely implements the WebTransport API over WebSockets for backwards compatibility. Also includes a NPM package.
• web-transport-trait defines an async trait, currently implemented by web-transport-quinn and web-transport-ws.
• web-transport-proto a bare minimum implementation of HTTP/3 just to establish the WebTransport session.