WebTransport.Client 0.1.3

WebTransport C# Client

WebTransport.Client is a general-purpose C# WebTransport client package targeting .NET Standard 2.1.

The package is designed to be usable from ordinary C# projects and Unity without exposing Unity-specific APIs.

Current Status

This repository contains the initial package architecture:

• managed WebTransport.Client API for sessions, streams, and datagrams
• managed WebTransport.Native P/Invoke wrapper
• stable native C ABI in native/webtransport_native
• MsQuic connection module with conditional build support
• HTTP/3 SETTINGS and WebTransport extended CONNECT scaffolding
• managed unit tests and opt-in interop tests

The native library uses MsQuic for QUIC/TLS transport. It can start a real connection with HTTP/3 ALPN (h3), send HTTP/3 client SETTINGS, send a minimally QPACK-encoded WebTransport extended CONNECT request, parse a simple response :status, open bidirectional WebTransport streams, route stream writes through MsQuic, and send/receive WebTransport datagrams through MsQuic datagrams. Managed ConnectAsync completes after the WebTransport session is accepted, and client-initiated stream/datagram receive APIs await native data events instead of requiring caller polling. Full peer SETTINGS parsing from live control streams, robust QPACK, and peer-initiated stream accept are still in progress.

Usage Shape

await using var client = new WebTransportClient();
await using WebTransportSession session = await client.ConnectAsync(
    new Uri("https://example.com/transport"));

await using WebTransportStream stream = await session.OpenBidirectionalStreamAsync();
await stream.WriteAsync(new byte[] { 1, 2, 3 });

await session.SendDatagramAsync(new byte[] { 4, 5, 6 });
WebTransportDatagram datagram = await session.ReceiveDatagramAsync();

ConnectAsync returns only after the remote endpoint accepts the WebTransport extended CONNECT request.

Packages

• WebTransport.Client: public API for C# consumers.
• WebTransport.Native: native loader and ABI wrapper.
• io.demiurgos.webtransport: Unity Package Manager package assembled from the same managed and native release artifacts.

Native runtime assets are expected under NuGet's standard layout:

runtimes/win-x64/native/webtransport_native.dll
runtimes/linux-x64/native/libwebtransport_native.so
runtimes/osx-arm64/native/libwebtransport_native.dylib
runtimes/android-arm64/native/libwebtransport_native.so
runtimes/ios/native/libwebtransport_native.a

Unity

Unity users should consume the same .NET Standard 2.1 managed assemblies as other C# users. The UPM package template lives under upm/io.demiurgos.webtransport, and generated release packages are written to artifacts/upm/io.demiurgos.webtransport.

WebGL is not supported by the native backend. A browser JavaScript backend would be a separate package.

Build

Managed build and tests:

dotnet test WebTransport.sln

The native backend requires MsQuic. Configure VCPKG_ROOT before building native presets.

Contributor Native Dependencies

This repo uses vcpkg manifest mode for native dependencies. Install vcpkg once somewhere under your user or developer tools directory:

mkdir $env:USERPROFILE\dev
git clone https://github.com/microsoft/vcpkg.git $env:USERPROFILE\dev\vcpkg
& "$env:USERPROFILE\dev\vcpkg\bootstrap-vcpkg.bat"
[Environment]::SetEnvironmentVariable("VCPKG_ROOT", "$env:USERPROFILE\dev\vcpkg", "User")
$env:VCPKG_ROOT = "$env:USERPROFILE\dev\vcpkg"

Then build the native library with MsQuic:

.\scripts\build-native.ps1 -Preset windows-msquic

The windows-msquic preset uses vcpkg.json to restore msquic. Release packages should use windows-msquic-release, which keeps MsQuic enabled and disables native test hooks.

With the MsQuic presets, Windows native outputs are written under:

artifacts/native-build-msquic/native/webtransport_native/Release/
artifacts/native-build-msquic-release/native/webtransport_native/Release/

Stage native runtime assets, pack NuGet packages, and assemble the UPM package:

.\scripts\Build-Packages.ps1 -Configuration Release -NativePreset windows-msquic-release -Rid win-x64

For local script validation without rebuilding native code:

.\scripts\Build-Packages.ps1 -Configuration Release -SkipNativeBuild -SkipTests -AllowMissingNativeAssets

NuGet packages are written to artifacts/nuget. The generated UPM package is written to artifacts/upm/io.demiurgos.webtransport.

For local NuGet publish from Windows, copy scripts/build-nuget-release.bat.example and scripts/push-nuget.bat.example to scripts/build-nuget-release.bat and scripts/push-nuget.bat, set your API key in push-nuget.bat, then run those scripts (they are gitignored).

For local interop tests, copy the built native library next to the test assembly:

Copy-Item artifacts/native-build-msquic/native/webtransport_native/Release/webtransport_native.dll `
  tests/WebTransport.Interop.Tests/bin/Debug/net8.0/ -Force

vcpkg manifest installs are local to the CMake build tree by default, under artifacts/native-build-msquic/vcpkg_installed. If vcpkg produces an additional runtime DLL for your triplet, copy that DLL next to webtransport_native.dll as well.

Run the opt-in MsQuic connection test:

$env:WEBTRANSPORT_MSQUIC_TEST_URL = "https://example.com/transport"
$env:WEBTRANSPORT_ALLOW_UNTRUSTED_CERTS = "1"
dotnet test WebTransport.sln

The opt-in test expects a native build linked with MsQuic and reports either a connection event or a meaningful transport/TLS failure. It does not yet establish a complete WebTransport session.