RTCDataChannel

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 RTCDataChannel interface represents a network channel which can be used for bidirectional peer-to-peer transfers of arbitrary data. Every data channel is associated with an RTCPeerConnection, and each peer connection can have up to a theoretical maximum of 65,534 data channels (the actual limit may vary from browser to browser).

To create a data channel and ask a remote peer to join you, call the RTCPeerConnection's createDataChannel() method. The peer being invited to exchange data receives a datachannel event (which has type RTCDataChannelEvent) to let it know the data channel has been added to the connection.

RTCDataChannel is a transferable object.

Instance properties

Also inherits properties from EventTarget.

binaryType: A string specifying the type of object that should be used to represent binary data received on the RTCDataChannel. Values are the same as allowed on the WebSocket.binaryType property: blob if Blob objects are being used, or arraybuffer if ArrayBuffer objects are being used. The default is blob.
bufferedAmount Read only: Returns the number of bytes of data currently queued to be sent over the data channel.
bufferedAmountLowThreshold: Specifies the number of bytes of buffered outgoing data that is considered "low". The default value is 0.
id Read only: Returns an ID number (between 0 and 65,534) which uniquely identifies the RTCDataChannel.
label Read only: Returns a string that contains a name describing the data channel. These labels are not required to be unique.
maxPacketLifeTime Read only: Returns the amount of time, in milliseconds, the browser is allowed to take to attempt to transmit a message, as set when the data channel was created, or null.
maxRetransmits Read only: Returns the maximum number of times the browser should try to retransmit a message before giving up, as set when the data channel was created, or null, which indicates that there is no maximum.
negotiated Read only: Indicates whether the RTCDataChannel's connection was negotiated by the Web app (true) or by the WebRTC layer (false). The default is false.
ordered Read only: Indicates whether or not the data channel guarantees in-order delivery of messages; the default is true, which indicates that the data channel is indeed ordered.
protocol Read only: Returns a string containing the name of the subprotocol in use. If no protocol was specified when the data channel was created, then this property's value is the empty string ("").
readyState Read only: Returns a string which indicates the state of the data channel's underlying data connection. It can have one of the following values: connecting, open, closing, or closed.

Obsolete properties

reliable Read only Deprecated Non-standard: Indicates whether or not the data channel is reliable.

Instance methods

Also inherits methods from EventTarget.

close(): Closes the RTCDataChannel. Either peer is permitted to call this method to initiate closure of the channel.
send(): Sends data across the data channel to the remote peer.

Events

bufferedamountlow: Sent when the number of bytes of data in the outgoing data buffer falls below the value specified by bufferedAmountLowThreshold.
close: Sent when the underlying data transport closes.
closing: Sent when the underlying data transport is about to start closing.
error: Sent when an error occurs on the data channel.
message: Sent when a message has been received from the remote peer. The message contents can be found in the event's data property.
open: Sent when the data channel is first opened, or when an existing data channel's underlying connection re-opens.

Data format

The underlying data format is defined by the IEEE specification SDP Offer/Answer Procedures for SCTP over DTLS Transport(RFC 8841). The current format specifies its protocol as either "UDP/DTLS/SCTP" (UDP carrying DTLS carrying SCTP) or "TCP/DTLS/SCTP" (TCP carrying DTLS carrying SCTP). Older browsers may only specify "DTLS/SCTP".

Example

const pc = new RTCPeerConnection();
const dc = pc.createDataChannel("my channel");

dc.onmessage = (event) => {
  console.log(`received: ${event.data}`);
};

dc.onopen = () => {
  console.log("datachannel open");
};

dc.onclose = () => {
  console.log("datachannel close");
};

Specifications

Specification
WebRTC: Real-Time Communication in Browsers # rtcdatachannel

Browser compatibility

BCD tables only load in the browser