Streaming a virtual terminal without video - html

Question

If I want to live broadcast some work on a text editor embedded in a virtual terminal on my personnal computer, I can stream on the web a video of the window containing it.
But since information consists mainly in a bunch of characters, possibly with some colors and formating, I think that video is a waste of ressources, bandwidth and technology speaking.
What would you recommend for this, and is there some server implementing the solution somewhere ?
The requirements are :
the stream must be almost real time (at least 1 update per second and no more than 1 second delay)
audience can access the stream with only a web browser (no additional software on their side), read-only (no interaction with the stream or with my terminal)
features from say xterm or urxvt be supported
all necessary software (both streamer client side and potential server side) are open source
Comments on technical advantages of such tool compared to video streaming are welcome.

Answer 1

I finally took the time to implement a complete solution, using socket.io within a simple NodeJS server for broadcasting.
On the client side, serve a simple HTML with an Xterm.js terminal
<script src='/socket.io/socket.io.js'></script>
<script src="xterm/xterm.js"></script>
...
<div class="terminal" id="terminal"></div>
and script the synchronization along the lines of
var socket = io();
term.open(document.getElementById('terminal'));
var updateTerminal = socket.on("updateTerminal", function(data) {
term.write(data);
});
Now the data that can be passed to term.write of Xterm.js can be raw terminal data. Several UNIX utilities can monitor such raw data from a terminal, for instance tmux as proposed by jerch in the comments, or script.
To pass these data to the server for broadcasting, the easiest way is to use a named pipe; so on the server side
mkfifo server_pipe
script -f server_pipe
(the terminal issuing that last command will be the one broadcasting; if one does not have physical access to the server, one can use an additional pipe and a tunneling connection
mkfifo local_pipe
cat local_pipe | ssh <server> 'cat > path/to/server_pipe'&
script -f local_pipe
)
Finally, the NodeJS server must be listening to the named pipe and broadcast any new data
/* create server */
const http = require('http');
const server = http.createServer(function (request, response) {
...
});
/* open named pipe for reading */
const fs = require('fs');
const fd = fs.openSync("path/to/server_pipe", 'r+')
const termStream = fs.createReadStream(null, {fd});
termStream.setEncoding('utf8');
/* broadcast any new data with socket.io */
const iolib = require("socket.io");
io = iolib(server);
termStream.on('data', function(data) {
io.emit("updateTerminal", data)
});
All this mechanism is implemented in my software Remote lecture.
As for the comparison with video broadcast, I did not take the time to actually quantify the difference, but for equivalent resolution and latency, the above mechanism should use much less network and computing resources than capturing a graphic terminal output and sharing it with video.