kwtransport: High-Performance WebTransport for Kotlin Multiplatform

kwtransport is a Kotlin Multiplatform library that provides a high-performance wrapper around the wtransport Rust crate, bringing WebTransport capabilities to your Kotlin applications across JVM, Android, and WebAssembly (WASM) targets. It aims to offer an idiomatic and robust Kotlin API for establishing WebTransport connections, managing streams, and handling datagrams with efficiency and ease.

Important

Disclaimer: This project is almost entirely LLM-generated (via Gemini). The author has no knowledge of Rust and relied on AI to bridge the gap between Kotlin and the underlying Rust implementation. While it is functional and tested, there may be unidiomatic Rust code or performance pitfalls.

Contributions are highly welcome! If you are a Rust expert or a Kotlin Multiplatform enthusiast, your help in refining the FFI bridge, improving memory management, or expanding target support would be greatly appreciated.

Features

• Kotlin Multiplatform: Write once, run on JVM, Android, and WASM.
• High Performance: Leverages the battle-tested wtransport Rust crate for underlying WebTransport protocol implementation.
• Asynchronous API: Built with Kotlin Coroutines and Flow for modern, non-blocking network operations.
• Clean Architecture: Designed with clear separation of concerns, making it easy to integrate into your projects.
• Reliable Stream & Datagram Handling: Provides intuitive APIs for unidirectional, bidirectional streams, and unreliable datagrams.
• TLS Certificate Management: Integrated handling for self-signed and trusted TLS certificates.

Installation

Maven Central

Add the dependency to your build.gradle.kts:

repositories {
    mavenCentral()
}

dependencies {
    implementation("io.github.arosov:kwtransport:0.0.2")
}

Note: The JVM artifact automatically includes runtime dependencies for all currently supported native platforms (linux-x64, macos-arm64, windows-x64). You do not need to manually add classifier dependencies unless you are targeting a specific platform exclusively to save space.

Supported Platforms

The following platforms are officially supported:

Platform	Architecture	Artifact Classifier	Notes
Linux	x86_64	linux-x64	Standard desktop/server Linux (Ubuntu, Debian, etc.)
macOS	ARM64	macos-arm64	Apple Silicon (M1/M2/M3)
Windows	x86_64	windows-x64	64-bit Windows
Android	ARM64, ARMv7, x86, x86_64	(bundled in AAR)	Handled automatically by Android Gradle Plugin
WASM	wasm-js	(bundled in Klib)	WebAssembly for Browser targets

Note: linux-arm64 and macos-x64 (Intel) are planned but not yet automatically built by the current CI pipeline.

Getting Started

To get started with kwtransport, ensure you have Java (JDK 17 or higher) and a recent version of the Kotlin Multiplatform plugin for Gradle installed.

Building the Project

To build the entire project:

./gradlew build

Running the CLI Chat Application

The cli-chat module provides a simple command-line chat application to demonstrate basic client-server communication using WebTransport streams.

1. Build the distribution (run once, or after code changes):

   ./gradlew :cli-chat:installDist

2. Run the server: Open a terminal and execute:

   ./cli-chat/build/install/cli-chat/bin/cli-chat -s

3. Run the client (in a new terminal):

   ./cli-chat/build/install/cli-chat/bin/cli-chat

   Type exit to close a chat session.

Running Tests

To run JVM tests for the kwtransport module:

./gradlew :kwtransport:cleanJvmTest :kwtransport:jvmTest

For other modules or specific targets, replace :kwtransport and :jvmTest as per the project's Gradle module conventions.

API Overview

The core of the kwtransport API resides in the kwtransport module, primarily within the io.github.arosov.kwtransport package. Key classes include:

• Endpoint: The entry point for creating client and server WebTransport endpoints.
• Connection: Represents an established WebTransport connection, allowing the opening and accepting of streams and sending/receiving datagrams.
• SendStream: For sending data over a WebTransport stream.
• RecvStream: For receiving data from a WebTransport stream, including a Flow<ByteArray> API for convenient consumption.
• Certificate: Utility for managing TLS certificates.
• KwTransportException and subclasses: Comprehensive exception hierarchy for robust error handling.

For detailed code examples demonstrating how to use these components, please see the Usage Examples documentation.

License

This project is licensed under the MIT License. See the LICENSE file for details.

Credits

kwtransport is built upon the excellent work of the wtransport Rust crate, an implementation of the WebTransport (over HTTP3) protocol.

wtransport Author: Biagio Festa wtransport Repository: https://github.com/BiagioFesta/wtransport

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