RTCDataChannel

BaselineWidely available *

This feature is well established and works across many devices and browser versions. It’s been available across browsers since January 2020.

* Some parts of this feature may have varying levels of support.

TheRTCDataChannel interface represents a network channel which can be used for bidirectional peer-to-peer transfers of arbitrary data. Every data channel is associated with anRTCPeerConnection, 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 theRTCPeerConnection'screateDataChannel() method. The peer being invited to exchange data receives adatachannel event (which has typeRTCDataChannelEvent) to let it know the data channel has been added to the connection.

RTCDataChannel is atransferable object.

Instance properties

Also inherits properties fromEventTarget.

binaryType: A string specifying the type of objectthat should be used to represent binary data received on theRTCDataChannel.Values are the same as allowed on theWebSocket.binaryType property:blob ifBlob objects are being used,orarraybuffer ifArrayBuffer objects are being used.The default isarraybuffer.
bufferedAmountRead only: Returns the number of bytes of datacurrently 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.
idRead only: Returns an ID number (between 0 and 65,534)which uniquely identifies theRTCDataChannel.
labelRead only: Returns a string that contains a name describing the data channel.These labels are not required to be unique.
maxPacketLifeTimeRead 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,ornull.
maxRetransmitsRead only: Returns the maximum number of timesthe browser should try to retransmit a message before giving up,as set when the data channel was created,ornull, which indicates that there is no maximum.
negotiatedRead only: Indicateswhether theRTCDataChannel's connection was negotiated by the Web app(true)or by the WebRTC layer (false).The default isfalse.
orderedRead only: Indicates whether or not the data channel guarantees in-order delivery of messages;the default istrue, which indicates that the data channel is indeed ordered.
protocolRead only: Returns a string containing the name of the subprotocol in use.If no protocol was specifiedwhen the data channel was created,then this property's value is the empty string ("").
readyStateRead only: Returns a stringwhich indicates the state of the data channel's underlying data connection.It can have one of the following values:connecting,open,closing, orclosed.

Obsolete properties

reliableRead onlyDeprecated Non-standard: Indicates whether or not the data channel isreliable.

Instance methods

Also inherits methods fromEventTarget.

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

Events

bufferedamountlow: Sentwhen the number of bytes of data in the outgoing data bufferfalls below the value specified bybufferedAmountLowThreshold.
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 foundin the event'sdata 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 specificationSDP 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");};