Serve
Overview

HTTP/3 and QUIC

Serving HTTP/3#

import serve, serve/reactor
 
serveH3Reactor(8443, tlsContext, handler)

QUIC needs its transport glue shim built and available on the loader path — the repo ships quic/build.sh for this.

Discovery from HTTP/1.1 and HTTP/2#

Browsers don't speak QUIC first; they discover it from a TCP response. Every TCP response from serveAllReactor carries Alt-Svc: h3=":<port>", which tells the browser HTTP/3 is available on the same port over UDP and lets it upgrade the next request on its own.

Request bodies and POST#

HTTP/3 server handlers receive (meth, path, headers, body) — POST bodies over QUIC are supported directly, not bolted on. See h3_post.nim and reactor_h3.nim.

WebTransport#

WebTransport runs over HTTP/3's extended CONNECT — see wt_echo.nim. It includes unreliable datagrams over QUIC per RFC 9221 (dgram_echo.nim), and bounded-resource overflow is counted rather than silently dropped — see wt_stream_echo.nim.

Conformance#

HTTP/3 support is checked against third-party interop — aioquic — rather than only against serve's own client, which catches spec deviations a self-test would miss.

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