WebSocketStream: opened property
Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.
Note: This feature is available in Web Workers.
The opened
read-only property of the
WebSocketStream
interface returns a Promise
that fulfills with an object once the socket connection is successfully opened. Among other features, this object contains a ReadableStream
and a WritableStream
instance for receiving and sending data on the connection.
Value
A promise, which fulfills with an object containing the following properties:
extensions
-
A string representing any extensions applied to the
WebSocketStream
. Such extensions are not currently defined, but may be in the future. Currently returns an empty string. protocol
-
A string representing the sub-protocol used to open the current WebSocket connection (chosen from the options specified in the
protocols
option of theWebSocketStream()
constructor). Returns an empty string if no sub-protocol has been used to open the connection (i.e. no sub-protocol options were included in the constructor call). readable
-
A
ReadableStream
instance. CallReadableStream.getReader()
on it to obtain aReadableStreamDefaultReader
instance that can be used to read incoming WebSocket data. writable
-
A
WritableStream
instance. CallWritableStream.getWriter()
on it to obtain aWritableStreamDefaultWriter
instance that can be used to write data to the WebSocket connection.
The promise rejects if the WebSocket connection fails.
Examples
const wsURL = "wss://127.0.0.1/";
const wss = new WebSocketStream(wsURL);
async function start() {
const { readable, writable, extensions, protocol } = await wss.opened;
const reader = readable.getReader();
const writer = writable.getWriter();
writer.write("ping");
while (true) {
const { value, done } = await reader.read();
if (done) {
break;
}
setTimeout(() => {
writer.write("ping");
}, 5000);
}
}
See Using WebSocketStream to write a client for a complete example with full explanation.
Specifications
Not currently a part of any specification. See https://github.com/whatwg/websockets/pull/48 for standardization progress.
Browser compatibility
BCD tables only load in the browser
See also
- WebSocketStream: integrating streams with the WebSocket API, developer.chrome.com (2020)