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RTCDataChannel.send

The send() method of the RTCDataChannel interface sends data across the data channel to the remote peer. This can be done any time except during the initial process of creating the underlying transport channel. Data sent before connecting is buffered if possible (or an error occurs if it's not possible), and is also buffered if sent while the connection is closing or closed.

Different browsers have different limitations on the size of the message you can send. Specifications exist to define how to automatically fragment large messages, but not all browsers implement them, and those that do have various additional restrictions. This will get less complicated over time, but for now, if you have questions, see Understanding message size limits in Using WebRTC data channels.

Syntax

RTCDataChannel.send(data);

Parameters

data: The data to transmit across the connection. This may be a USVString, a Blob, an ArrayBuffer, or an ArrayBufferView.

Return value

undefined.

Exceptions

InvalidStateError: Since the data channel uses a separate transport channel from the media content, it must establish its own connection; if it hasn't finished doing so (that is, its readyState is "connecting"), this error occurs without sending or buffering the data.
NetworkError: The specified data would need to be buffered, and there isn't room for it in the buffer. In this scenario, the underlying transport is immediately closed.
TypeError: The specified data is too large for the other peer to receive. Since there are multiple techniques for breaking up large data into smaller pieces for transfer, it's possible to encounter scenarios in which the other peer does not support the same ones. For example, if one peer is a modern browser that supports using the EOR (End of Record) flag to indicate when a received message is the last piece of a multi-part object sent using send(). For more information about message size restrictions, see Understanding message size limits in Using WebRTC data channels.

Example

In this example, a routine called sendMessage() is created; it accepts an object as input and sends to the remote peer, over the RTCDataChannel, a JSON string with the specified object and a time stamp.

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

function sendMessage(msg) {
  let obj = {
    "message": msg,
    "timestamp": new Date()
  }
  dc.send(JSON.stringify(obj));
}

Specifications

Specification	Status	Comment
WebRTC 1.0: Real-time Communication Between Browsers The definition of 'RTCDataChannel.send()' in that specification.	Working Draft	Initial specification.

Browser compatibility

Feature	Chrome	Firefox (Gecko)	Internet Explorer	Opera	Safari
Basic support	23	22 (22) [1]	No support	(Yes)	?

Feature	Android Webview	Chrome for Android	Firefox Mobile (Gecko)	IE Mobile	Opera Mobile	Safari Mobile
Basic support	?	29	22 (22) [1]	No support	?	?

[1] The interface is called DataChannel and not RTCDataChannel in Firefox. However, a binding has been in place since Firefox 24 so that either name will work.