How to broadcast media stream using SignalR - sockets

Question

We are trying to build .net core app to share screen or window. But it doesn't work.
The code is like this:
Html file:
<div class="container">
<div class="row p-1">
<h1>WebRTC Screen Sharing Demo</h1>
<hr>
<button onclick="captureScreen()">Capture</button>
<video id="local-video" muted autoplay></video>
</div>
</div>
<script src="~/js/signalr/dist/browser/signalr.js"></script>
<script src="~/js/stream.js"></script>
Stream.js:
"use strict";
var connection = new signalR.HubConnectionBuilder().withUrl("/streamHub").build();
connection.start().then(function () {
console.log("Connection started");
}).catch(function (err) {
return console.error(err.toString());
});
connection.on("ClientReceiveStream", function (stream) {
document.getElementById("local-video").srcObject = stream; // I need to set the video source to the media stream.
});
async function captureScreen() {
let mediaStream = null;
try
{
mediaStream = await navigator.mediaDevices.getDisplayMedia({
video:
{
cursor: "always"
},
audio: false
});
//Im trying to send the media stream to the server
connection.invoke("ServerSendStream", mediaStream).catch(function (err)
{
return console.error(err.toString());
});
} catch (ex) {
console.log("Error occurred", ex);
}
}
The hub:
public class StreamHub : Hub
{
public async Task ServerSendStream(object mediaStream) // I need to get the media stream here
{
await Clients.All.SendAsync("ClientReceiveStream", mediaStream);
}
}
How can we send this mediaStream object to the server, and then broadcast it?

Answer 1

There is no way to broadcast a stream to a client. The client needs to ask the server for a stream of data.
See the docs on how to do this: https://learn.microsoft.com/aspnet/core/signalr/streaming?view=aspnetcore-7.0#server-to-client-streaming-2
And when consuming the data on the client-side, you'll need to create some sort of stream and add the data to it, probably similar to the example in https://developer.mozilla.org/en-US/docs/Web/API/MediaSource