Running a Client

To dial a WebTransport session, initialize a webtransport.Transport, and call the Dial function.

var d webtransport.Transport
// optionally, add custom headers
headers := http.Header{}
headers.Add("foo", "bar")
rsp, sess, err := d.Dial(ctx, "https://example.com/webtransport", headers)
// err is only nil if rsp.StatusCode is a 2xx
// Handle the session. Here goes the application logic.

This initiates a new WebTransport session with the server by sending an Extended CONNECT request to the server. The server might reject this request, in which case the status code of the HTTP response will not be in the 2xx range.

The parameters for the underlying QUIC connection can be adjusted by setting the QUICConfig on the Transport. A custom config must enable datagram support using quic.Config.EnableDatagrams, and stream resets with partial delivery using quic.Config.EnableStreamResetPartialDelivery.

Application Protocol Negotiation

A client can advertise WebTransport application protocols by setting ApplicationProtocols on the Transport. This is the WebTransport-specific negotiation described in the Application Protocol Negotiation section of the WebTransport over HTTP/3 draft, not TLS ALPN.

d := webtransport.Transport{
    ApplicationProtocols: []string{"foo", "bar"},
}

_, sess, err := d.Dial(ctx, "https://example.com/webtransport", nil)
// ... error handling

selected := sess.SessionState().ApplicationProtocol
if selected == "" {
    // The server accepted the session without selecting an application protocol.
}

If the server selects one of the offered protocols, it is available through sess.SessionState().ApplicationProtocol. If the server accepts the session without selecting a protocol, ApplicationProtocol is empty.

Reusing a QUIC Connection

To reuse an established QUIC connection, call Transport.NewClientConn. The returned ClientConn can create multiple WebTransport sessions using Dial, and send regular HTTP requests using RoundTrip. The application is responsible for closing the QUIC connection when it is no longer needed.

📝 Future Work

Allow Optimistic Opening of Streams: #136

Running a Server Session