Locust aiohttp web browser performance testing

Question

I wrote a websocket server using the python aiohttp library.

Now I'm trying to test the performance using locust and a fragment , but the locust cannot open more than 2000 connections (websocket.create_connection () causes an error: [Errno 104] Connection reset by peer).

I do not understand where the problem is. Is the locust unable to open so many connections, or aiohttp cannot handle so many connections (but it does not write any errors), or maybe ubuntu resets the new connections (I set ulimit to 1,000,000, but the CPU usage is almost 100%).