Connection Debugger & Transport Finder
“Why can’t I connect?” bisected layer by layer, and “polling, SSE, WebSockets or HTTP/3?” — answer the questions and get a diagnosis or a recommendation with reasons.
The server has news. Pick the transport by direction, frequency, what sits between the browser and the server, and how lossy the client’s link is — not by what is fashionable. The finder starts from the boring answer and only leaves it when a specific constraint forces the move.
Step 1
Which way does the data need to flow?
"The client also sends" only counts if it sends often and latency matters; a click every few minutes is a normal HTTP request.