websocat | line client for WebSockets , like netcat | Websocket library

I'm trying to create a websocket server (and HTTP, hence using warp) that forwards messages from one source (an MQTT subscription) to many clients over websockets. This mostly seems to work fine, aside from the clients not receiving the first websocket message until the second message has been broadcast; then always staying one message behind until finally never receiving the last message. To me, the problem seems to be a send buffer that never fully flushes in the ws_connected function.

I use futures::stream::iter to turn the BusReader into a stream, then map the messages into the required Ok(Message) type that the WebSocket Sink requires. The official warp websocket chat example uses a similar construct for forwarding between streams: https://github.com/seanmonstar/warp/blob/42fd14fdab8145d27ae770fe4b5c843a99bc2a44/examples/websockets_chat.rs#L62.

In this pared-down example, the server broadcasts the values 0-9 over the bus. A websocat client (and JS websocket client in Firefox) receives the messages 0-8 -- albeit always one behind the broacast and server's stdout -- but 9 never arrives. The async_bus_print function receives all of the values on time, however, which proves that the messages are at least passing through the Bus with no problem.

Here is the server process's output:

I'm trying to use the library https://github.com/AnthumChris/opus-stream-decoder/

I have a stream of OPUS encoded sound (2ch, 48kHz) from a high quality microphone (but I play a music in loop on it to test this). I know it works because I can hear it if I use:

websocat --binary ws://third-i.local/api/sound - | mpv -

(It's opening the websocket and streaming its output to mpv (mplayer)).

But when I play in the browser all I hear is very small parts of the sound every second or so. But the sound itself sounds good (I believe it is a very small part of the music).

Here is the JS code I wrote to listen in the browser:

I know how to broadcast but i can not target clients. Here is my script:

I can't find a solution for more than a week. Everything works fine on the dev server, but not on production. I have no strength, I appeal to you, colleagues :)

I'm using Laravel-echo-server on Socket.io using CloudFlare. When trying to connect, I get an error: WebSocketError: Unexpected status code received (502 Bad Gateway)

Ubuntu 16.04.7 LTS, Laravel Echo Server: 1.6.1, NodeJs: v12.19.0

laravel-echo-server.json: