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WebRTC Publishing

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About WebRTC

WebRTC is a P2P protocol of communication between two clients over an already established connection. For example, to communicate with each other by WebRTC, two browsers need to be connected by opening the same website in the Internet. Connection can also be established by means of a mediator, so-called signaling server.

So there are two clients and a signaling server that connects these clients. Before starting to transmit video data, the clients need to establish the connection. To do so, they exchange data of two types about the connection:

  • Textual descriptions of media streams in the SDP format
  • ICE Candidates as part of an SDP

The signaling server (the mediator) makes it possible to transfer the data about the connection from one client to the other.

WebRTC is the ideal for webinars, online communication, video chats.

For more details, see Using WebRTC protocol.


  • Configure HTTPS. Some browsers allow video and audio publishing through WebRTC by using secure connection only. The browser might deny access to the camera and microphone from a page located not by HTTPS but by HTTP address. But this is allowed on local addresses (localhost,
  • Do not close UDP ports. Flussonic does not have a fixed port range for WebRTC, i.e. the ports allocated by the OS are used. When closing UDP ports, you can accidentally close the ones that are being used. Consider not using any other software on the Flussonic server to safely allow UDP listening on all ports.

How to organize publication using WebRTC

On the Flussonic server, add a published stream to the configuration, this is a stream with the source publish://.

stream published {
  input publish://;

You can also add a stream through the Flussonic UI:

  1. Head to Media tab and add a stream clicking on Add button next to the Streams section.
  2. Then in the stream settings go to the Input tab and specify `publish://`` in the URL field. Make sure that Published input is accept:

Flussonic stream mixing

Published input accept

Now the code must be run on the client side that publishes video to the created stream. To write the code use the Flussonic WebRTC player library.

To configure publishing through WebRTC:

  • Head to options on the same Input tab:


  • Set the necessary values:

WebRTC settings

Installing the library components via NPM and webpack

To import our library to your project with webpack, download the package:

npm install --save @flussonic/flussonic-webrtc-player

Then import components to your application:

import {
} from "@flussonic/flussonic-webrtc-player";

The description of the library classes can be found at npm.

See also the demo application, which code is also found further on this page.

Installing the library components without NPM and webpack

Add this line to the script section of your HTML page:

<script src=""></script>

The example of a webpage containing the player code is further on this page.

WebRTC publication options

Audio podcasts through WebRTC

To publish only the audio track without video, in the options of the publisher instance use the following configuration in constraints:

import Publisher from '../publisher';
publisher = new Publisher(

    constraints: {
      video: false,
      audio: true,

If you omit the option video altogether, the result will be the same — only the audio track will be published to Flussonic.

To play such a stream, no additional configuring is needed.

Muting a publication

To mute a publication, use the mute method:

import Publisher from '../publisher';
publisher = new Publisher(*your options*);

If you bind the mute method to a button in your client app, the user will be able to disable the sound in the output stream during its publishing. The demo application has an example of such a button.

Capturing screen

WebRTC player allows to publish captured screen that can be useful for demonstrations. To do this, use the shareScreen method:

import Publisher from '../publisher';
publisher = new Publisher(*your options*);

To switch back to capturing video from camera, use this method once again. If you bind the shareScreen method to a button in your client app, the user will be able to switch to capturing a screen and back to capturing form a camera during publishing.

Publishing streams via WHIP

For a long time, WebRTC has not been adopted in broadcasting and streaming industry because it has no standard signaling protocol and is too complex to be implemented in broadcasting tools and applications. To solve this problem, a new WHIP protocol was designed.

WHIP (WebRTC-HTTP ingest protocol) provides a simple and media server-agnostic way of injecting WebRTC streams that can be easily integrated in existing broadcasting tools. The whole WebRTC negotiation process in WHIP can be reduced to an HTTP POST request to send the SDP offer, and a 200/202 response from the media server to return the SDP answer instead. At the same time, WHIP keeps all the advantages of WebRTC such as low latency, resilience, bandwidth adaptation, encryption, supporting common codecs, adaptive bitrate, and so on.


This protocol works similarly to WHAP that is used for playing streams.

Flussonic Media Server allows you to publish streams via WHIP. It does not require any specific configuration for it. Just follow the steps described above for publishing via WebRTC.

Use the following URL for the published stream in your application:


See Streaming API reference.