RTCDataChannel: readyState property

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 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

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

Browser compatibility

See also

• WebRTC
• Using WebRTC data channels
• RTCDataChannel
• createDataChannel()