On WebSocket server, can't cross a certain number of concurrent connections

Hello @walkor

On the same machine I can get up to 200k req/s for `workerman` HTTP server, however I cannot get more than `28,232` for WebSocket simple echo server! 🤔

I tested with normal event loop, and libevent, no difference except for errors when using Select.

What might be the problem! 🤔

Start by reproducing the WebSocket simple echo server's 28,232-connection limit on the same machine, then compare it with the HTTP server under the normal event loop and libevent. Also check the Select run and its reported errors. Done means the limiting behavior is explained and the issue has a confirmed, actionable direction.

Written by the indexing model from the issue text.