RTCDataChannel: readyState 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 readyState returns a string which indicates the state of the data channel's underlying data connection.

Values

A string indicating the current state of the underlying data transport, which is one of the following values:

connecting

The user agent (browser) is in the process of creating the underlying data transport; this is the state of a new RTCDataChannel after being created by RTCPeerConnection.createDataChannel(), on the peer which started the connection process.

open

The underlying data transport has been established and data can be transferred bidirectionally across it. This is the default state of a new RTCDataChannel created by the WebRTC layer when the remote peer created the channel and delivered it to the site or app in a datachannel event.

closing

The process of closing the underlying data transport has begun. It is no longer possible to queue new messages to be sent, but previously queued messages may still be send or received before entering the closed state.

closed

The underlying data transport has closed, or the attempt to make the connection failed.

Example

js
const dataChannel = peerConnection.createDataChannel("File Transfer");
const sendQueue = [];
function sendMessage(msg) {
  switch (dataChannel.readyState) {
    case "connecting":
      console.log(`Connection not open; queueing: ${msg}`);
      sendQueue.push(msg);
      break;
    case "open":
      sendQueue.forEach((msg) => dataChannel.send(msg));
      break;
    case "closing":
      console.log(`Attempted to send message while closing: ${msg}`);
      break;
    case "closed":
      console.log("Error! Attempt to send while connection closed.");
      break;
  }
}

Specifications

Specification
WebRTC: Real-Time Communication in Browsers
# dom-datachannel-readystate

Browser compatibility

See also