RTCDataChannel

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.

Properties

Also inherits properties from: EventTarget

binaryType

The property binaryType on the RTCDataChannel interface is a DOMString which specifies the type of JavaScript object which should be used to represent binary data received on the RTCDataChannel. Values allowed by the WebSocket.binaryType property are also permitted here: "blob" if Blob objects are being used or "arraybuffer" if ArrayBuffer objects are being used. The default is "blob".

bufferedAmount Read only

The read-only RTCDataChannel property bufferedAmount returns the number of bytes of data currently queued to be sent over the data channel.

bufferedAmountLowThreshold

The RTCDataChannel property bufferedAmountLowThreshold is used to specify the number of bytes of buffered outgoing data that is considered "low." The default value is 0.

id Read only

The read-only RTCDataChannel property id returns an ID number (between 0 and 65,534) which uniquely identifies the RTCDataChannel.

label Read only

The read-only RTCDataChannel property label returns a DOMString containing a name describing the data channel. These labels are not required to be unique.

maxPacketLifeTime Read only

The read-only RTCDataChannel property maxPacketLifeTime 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

The read-only RTCDataChannel property maxRetransmits returns the maximum number of times the browser should try to transmit a message before giving up when in unordered mode, as set when the data channel was created, or null, which indicates that there is no maximum.

negotiated Read only

The read-only RTCDataChannel property negotiated indicates whether the RTCDataChannel's connection was negotiated by the Web app (true) or by the WebRTC layer (false). false

ordered Read only

The read-only RTCDataChannel property ordered 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

The read-only RTCDataChannel property protocol returns a DOMString 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

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

reliable Read only

The read-only RTCDataChannel property reliable indicates whether or not the data channel is reliable.

stream Read only

The deprecated (and never part of the official specification) read-only RTCDataChannel property stream returns an ID number (between 0 and 65,535) which uniquely identifies the RTCDataChannel.

Event handlers

Also inherits event handlers from: EventTarget

onbufferedamountlow

The RTCDataChannel.onbufferedamountlow property is an EventHandler which specifies a function the browser calls when the bufferedamountlow event is sent to the RTCDataChannel. This event, which is represented by a simple Event object, is sent when the amount of data buffered to be sent falls to or below the threshold specified by the channel's bufferedAmountLowThreshold.

onclose

The RTCDataChannel.onclose property is an EventHandler which specifies a function to be called by the browser when the close event is received by the RTCDataChannel. This is a simple Event which indicates that the data channel has closed down.

onerror

The RTCDataChannel.onerror property is an EventHandler which specifies a function to be called when the error event is received. When an error occurs on the data channel, the function receives as input an ErrorEvent object describing the error which occurred.

onmessage

The RTCDataChannel.onmessage property stores an EventHandler which specifies a function to be called when the message event is fired on the channel. This event is represented by the MessageEvent interface. This event is sent to the channel when a message is received from the other peer.

onopen

The RTCDataChannel.onopen property is an EventHandler which specifies a function to be called when the open event is fired; this is a simple Event which is sent when the data channel's underlying data transport—the link over which the RTCDataChannel's messages flow—is established or re-established.

Methods

Also inherits methods from: EventTarget

close()

The RTCDataChannel.close() method closes the RTCDataChannel. Either peer is permitted to call this method to initiate closure of the channel.

send()

The send() method of the RTCDataChannel interface sends data across the data channel to the remote peer.

Data format

The underlying data format is defined by the IEEE draft specification draft-ietf-mmusic-sctp-sdp. 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

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

dc.onmessage = function (event) {
  console.log("received: " + event.data);
};

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

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

Specifications

Specification	Status	Comment
WebRTC 1.0: Real-time Communication Between Browsers The definition of 'RTCDataChannel' in that specification.	Candidate Recommendation	Initial specification.

Browser compatibilityUpdate compatibility data on GitHub

	Desktop
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari
Basic support	Yes	?	24 24 22 — 60 Uses the non-standard name: DataChannel	No	Yes	?
binaryType	Yes	?	22	No	Yes	?
bufferedAmount	56	?	No	No	43	No
bufferedAmountLowThreshold	56	?	No	No	43	No
close	56	?	No	No	43	No
id	56	?	No	No	43	No
label	56	?	No	No	43	No
maxPacketLifeTime	56	?	No	No	43	No
maxRetransmits	56	?	No	No	43	No
negotiated	56	?	No	No	43	No
ordered	56	?	No	No	43	No
protocol	56	?	No	No	43	No
onbufferedamountlow	57 57 The default for rtcpMuxPolicy is require.	?	?	?	44 44 The default for rtcpMuxPolicy is require.	?
onclose	56	?	No	No	43	No
onerror	56	?	No	No	43	No
onmessage	56	?	No	No	43	No
onopen	56	?	No	No	43	No
priority	?	?	?	?	?	?
readyState	56	?	No	No	43	No
reliable	56	?	No	No	43	No
Support for sctp-sdp-21 format	58	?	63	No	?	No
send	56	?	No	No	43	No
stream	56	?	No	No	43	No

	Mobile
	Android webview	Chrome for Android	Edge Mobile	Firefox for Android	Opera for Android	iOS Safari	Samsung Internet
Basic support	4.4	29	?	24 24 22 — 60 Uses the non-standard name: DataChannel	Yes	No	Yes
binaryType	4.4	29	?	22	Yes	No	Yes
bufferedAmount	56	56	?	No	43	?	6.0
bufferedAmountLowThreshold	56	56	?	No	43	?	6.0
close	56	56	?	No	43	?	6.0
id	56	56	?	No	43	?	6.0
label	56	56	?	No	43	?	6.0
maxPacketLifeTime	56	56	?	No	43	?	6.0
maxRetransmits	56	56	?	No	43	?	6.0
negotiated	56	56	?	No	43	?	6.0
ordered	56	56	?	No	43	?	6.0
protocol	56	56	?	No	43	?	6.0
onbufferedamountlow	57 57 The default for rtcpMuxPolicy is require.	57 57 The default for rtcpMuxPolicy is require.	?	?	44 44 The default for rtcpMuxPolicy is require.	?	7.0
onclose	56	56	?	No	43	?	6.0
onerror	56	56	?	No	43	?	6.0
onmessage	56	56	?	No	43	?	6.0
onopen	56	56	?	No	43	?	6.0
priority	?	?	?	?	?	?	?
readyState	56	56	?	No	43	?	6.0
reliable	56	56	?	No	43	?	6.0
Support for sctp-sdp-21 format	58	58	?	63	?	?	?
send	56	56	?	No	43	?	6.0
stream	56	56	?	No	43	?	6.0

See also

• WebRTC API