RTCDataChannel.readyState

The read-only RTCDataChannel property readyState returns an enum of type RTCDataChannelState which indicates the state of the data channel's underlying data connection.

Syntax

var state = aDataChannel.readyState;

Values

A string which is one of the values in the RTCDataChannelState enum, indicating the current state of the underlying data transport.

RTCDataChannelState enum

The RTCDataChannelState enum defines string constants which reflect the current status of the RTCDataChannel's underlying data connection.

Constant	Description
"connecting"	The user agent (browser) is in the process of creating the underlying data transport; that is, whatever network level connection is used to link the two peers together is in the process of being set up. 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 to the site or app in a datachannel event of type RTCDataChannelEvent.
"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

var dataChannel = peerConnection.createDataChannel("File Transfer");
var 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	Status	Comment
WebRTC 1.0: Real-time Communication Between Browsers The definition of 'RTCDataChannel.readyState' in that specification.	Working Draft	Initial specification.

Browser compatibility

[1] The interface is called DataChannel and not RTCDataChannel in Firefox; however, a binding was added in Firefox 24 which allows either name to be used.

See also

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