RTCDataChannel: bufferedAmount property
Baseline
Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since January 2020.
The read-only RTCDataChannel property
bufferedAmount returns the number of bytes of data
currently queued to be sent over the data channel. The queue may build up as a
result of calls to the send() method. This only
includes data buffered by the user agent itself; it doesn't include any framing overhead
or buffering done by the operating system or network hardware.
The user agent may implement the process of actually sending data in any way it chooses; this may be done periodically during the event loop or truly asynchronously. As messages are actually sent, this value is reduced accordingly.
Note:
Closing the data channel doesn't reset this count, even though the user agent purges
the queued messages. However, even after closing the channel, attempts to send
messages continue to add to the bufferedAmount value, even though the
messages are neither sent nor buffered.
Whenever this value decreases to fall to or below the value specified in the
bufferedAmountLowThreshold
property, the user agent fires the bufferedamountlow event. This event may
be used, for example, to implement code which queues more messages to be sent whenever
there's room to buffer them.
Value
The number of bytes of data currently queued to be sent over the data channel but have not yet been sent.
Example
The snippet below includes a function which changes the contents of a block with the ID
"bufferSize" to a string indicating the number of bytes currently buffered on an
RTCDataChannel.
const dc = peerConnection.createDataChannel("File Transfer");
// …
function showBufferedAmount(channel) {
const el = document.getElementById("bufferSize");
el.innerText = `${channel.bufferedAmount} bytes`;
}
Specifications
| Specification |
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| WebRTC: Real-Time Communication in Browsers # dom-datachannel-bufferedamount |
Browser compatibility
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bufferedAmount
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