WebTransport
Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.
The WebTransport
interface of the WebTransport API provides functionality to enable a user agent to connect to an HTTP/3 server, initiate reliable and unreliable transport in either or both directions, and close the connection once it is no longer needed.
Note: This feature is available in Web Workers
Constructor
WebTransport()
-
Creates a new
WebTransport
object instance.
Instance properties
closed
Read only- : Returns a promise that resolves when the transport is closed.
datagrams
Read only- : Returns a
WebTransportDatagramDuplexStream
instance that can be used to send and receive datagrams.
- : Returns a
congestionControl
Read only Experimental- : Returns a string that indicates the application preference for either high throughput or low-latency when sending data.
incomingBidirectionalStreams
Read only- : Represents one or more bidirectional streams opened by the server. Returns a
ReadableStream
ofWebTransportBidirectionalStream
objects. Each one can be used to read data from the server and write data back to it.
- : Represents one or more bidirectional streams opened by the server. Returns a
incomingUnidirectionalStreams
Read only- : Represents one or more unidirectional streams opened by the server. Returns a
ReadableStream
ofWebTransportReceiveStream
objects. Each one can be used to read data from the server.
- : Represents one or more unidirectional streams opened by the server. Returns a
ready
Read only- : Returns a promise that resolves when the transport is ready to use.
reliability
Read only Experimental- : Returns a string that indicates whether the connection supports reliable transports only, or whether it also supports unreliable transports (such as UDP).
Instance methods
close()
-
Closes an ongoing WebTransport session.
createBidirectionalStream()
-
Asynchronously opens a bidirectional stream (
WebTransportBidirectionalStream
) that can be used to read from and write to the server. createUnidirectionalStream()
-
Asynchronously opens a unidirectional stream (
WritableStream
) that can be used to write to the server. getStats()
Experimental-
Asynchronously returns a
Promise
that fulfills with an object containing HTTP/3 connection statistics.
Examples
The example code below shows how you'd connect to an HTTP/3 server by passing its URL to the WebTransport()
constructor.
Note that the scheme needs to be HTTPS, and the port number needs to be explicitly specified.
Once the WebTransport.ready
promise fulfills, you can start using the connection.
js
async function initTransport(url) {
// Initialize transport connection
const transport = new WebTransport(url);
// The connection can be used once ready fulfills
await transport.ready;
return transport;
}
You can respond to the connection closing by waiting for the WebTransport.closed
promise to fulfill.
Errors returned by WebTransport
operations are of type WebTransportError
, and contain additional data on top of the standard DOMException
set.
The closeTransport()
method below shows a possible implementation.
Within a try...catch
block it uses await
to wait for the closed
promise to fulfill or reject, and then reports whether or not the connection closed intentionally or due to error.
js
async function closeTransport(transport) {
// Respond to connection closing
try {
await transport.closed;
console.log(`The HTTP/3 connection to ${url} closed gracefully.`);
} catch (error) {
console.error(`The HTTP/3 connection to ${url} closed due to ${error}.`);
}
}
We might call the asynchronous functions above in their own asynchronous function, as shown below.
js
// Use the transport
async function useTransport(url) {
const transport = await initTransport(url);
// Use the transport object to send and receive data
// ...
// When done, close the transport
await closeTransport(transport);
}
const url = "https://example.com:4999/wt";
useTransport(url);
For other example code, see the individual property and method pages.
Specifications
Specification |
---|
WebTransport # web-transport |
Browser compatibility
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