effect-webtransport

WebTransport sessions, streams, and datagrams as Effect services.

npm install effect-webtransport "effect@^4.0.0-rc.115"

Requires a platform WebTransport implementation. The constructor is an injectable service for platforms and tests.

import { Effect } from "effect";
import { WebTransport } from "effect-webtransport";

const program = Effect.gen(function* () {
  const session = yield* WebTransport.connect("https://example.com/wt");
  const stream = yield* session.openBidirectionalStream();
  const write = yield* WebTransport.writer(stream.writable);

  yield* write(new TextEncoder().encode("hello"));
}).pipe(Effect.scoped, Effect.provide(WebTransport.layerConstructorGlobal));

Closing the scope closes the session and its streams, including on interruption. Datagrams are unreliable; use reliable streams when delivery matters.

• WebTransport provides sessions, streams, datagrams, and typed errors.
• WebTransportSocket adapts one bidirectional stream to Effect's scoped Socket.reader and Socket.writer. Pulls apply backpressure; every close, including peer FIN, fails with SocketCloseError. RPC needs self-delimiting serialization such as RpcSerialization.layerNdjson or layerSchemaBinary().
• Fallback selects WebTransport or WebSocket before application traffic. It never replays requests or switches an active session to another transport.

With Effect RC 115, replace socket.run(handler) with a scoped reader loop:

const consume = Effect.gen(function* () {
  const { pull } = yield* socket.reader;
  const writer = yield* socket.writer;

  yield* writer.write("hello");
  while (true) {
    for (const frame of yield* pull) {
      yield* handle(frame);
    }
  }
}).pipe(Effect.scoped);

Handle SocketError close reasons around this loop, or use Effect.retry to acquire a fresh reader. The closeCodeIsError option has been removed.

Cloudflare support is described by effect-cf's WebTransport module.

Changelog · MIT license