A high-performance WebTransport implementation built on MsQuic.
libwtf implements WebTransport over HTTP/3 (draft-07) with forward compatibility for draft-13. The library handles real-world browser quirks where Chrome sends draft-02 format without proper negotiation.
WebTransport provides low-latency, bidirectional communication over QUIC with support for both reliable streams and unreliable datagrams. All communication occurs over a single QUIC connection with built-in congestion control and multiplexing.
The library centers around session management with isolated WebTransport sessions. Applications handle connection validation, session lifecycle events, and stream management through callback-based APIs.
Stream support includes both bidirectional and unidirectional channels with flow control and priority handling. Datagram support enables low-latency messaging for real-time applications.
The implementation provides comprehensive error handling with detailed diagnostics and performance statistics for monitoring connection health and throughput.
Status: Early development - not recommended for production use.
# Build from source
git clone https://github.com/andrewmd5/libwtf.git
cd libwtf
# macOS / Linux
cmake -DWTF_BUILD_SAMPLES=on -S . -B build -G "Ninja Multi-Config"
# Windows
cmake -S . -B build -G "Visual Studio 17 2022"
cmake --build build --config Release#include "wtf.h"
void session_callback(const wtf_session_event_t *event) {
switch (event->type) {
case WTF_SESSION_EVENT_CONNECTED:
printf("Session established\n");
break;
case WTF_SESSION_EVENT_DATAGRAM_RECEIVED:
// Echo datagram back
wtf_session_send_datagram(event->session, &event->datagram_received.data);
break;
}
}
int main() {
// Initialize context
wtf_context_config_t ctx_config = {.log_level = WTF_LOG_INFO};
wtf_context_t *context;
wtf_context_create(&ctx_config, &context);
// Configure server
wtf_server_config_t config = {
.port = 4433,
.cert_file = "server.crt",
.key_file = "server.key",
.session_callback = session_callback
};
// Start server
wtf_server_t *server;
wtf_server_create(context, &config, &server);
wtf_server_start(server);
// Server runs...
wtf_server_destroy(server);
wtf_context_destroy(context);
}void stream_callback(const wtf_stream_event_t *event) {
switch (event->type) {
case WTF_STREAM_EVENT_DATA_RECEIVED:
// Echo data back
wtf_stream_send(event->stream, event->data_received.buffers,
event->data_received.buffer_count, false);
break;
case WTF_STREAM_EVENT_PEER_CLOSED:
printf("Stream closed by peer\n");
break;
}
}
// In session callback:
case WTF_SESSION_EVENT_STREAM_OPENED:
wtf_stream_set_callback(event->stream_opened.stream, stream_callback);
break;// Create outbound stream
wtf_stream_t *stream;
wtf_result_t result = wtf_session_create_stream(session, WTF_STREAM_BIDIRECTIONAL, &stream);
if (result == WTF_SUCCESS) {
// Send initial data
const char *message = "Hello from server";
wtf_buffer_t buffer = {.data = (uint8_t*)message, .length = strlen(message)};
wtf_stream_send(stream, &buffer, 1, false);
}wtf_connection_decision_t connection_validator(const wtf_connection_request_t *request, void *user_data) {
printf("Connection from: %s%s\n",
request->authority ? request->authority : "unknown",
request->path ? request->path : "/");
// Validate origin, check authentication, etc.
if (request->origin && strcmp(request->origin, "https://example.com") == 0) {
return WTF_CONNECTION_ACCEPT;
}
return WTF_CONNECTION_REJECT;
}The library provides comprehensive error handling with detailed diagnostics:
wtf_result_t result = wtf_server_start(server);
if (result != WTF_SUCCESS) {
printf("Server start failed: %s\n", wtf_result_to_string(result));
return -1;
}
// Get detailed error information
wtf_error_details_t details;
if (wtf_get_error_details(error_code, &details) == WTF_SUCCESS) {
printf("Error: %s (code: %u)\n", details.description, details.error_code);
}Included with libwtf is a complete echo server that demonstrates session management, stream handling, datagram processing, and command parsing. The server supports interactive commands for testing WebTransport features.
./example_server --port 4433 --cert server.crt --key server.key --verboseWebTransport runs over QUIC with HTTP/3 framing. The implementation handles QPACK header compression, flow control, and connection migration. Session multiplexing allows multiple WebTransport sessions over a single QUIC connection.
Browser compatibility varies significantly. Chrome supports WebTransport but with draft-02 semantics, while Firefox implementation is still evolving. The library includes compatibility shims for real-world deployment.
Future client implementation will provide matching functionality for WebTransport clients, enabling full-duplex communication patterns.
Feedback and contributions welcome!