WebSocket capability test (disposable — delete after use)

Endpoint:

1. Single connection — upgrade, echo, ping/pong, persistence

2. Concurrent connections

4 (one match) 10 20

3. Idle connection — finds a proxy timeout

open a silent connection — the server sends nothing on this one, so if it dies, a timeout killed it.

Leave this page open for at least 5 minutes. A connection that survives that, with heartbeats arriving, is a connection this hosting can carry.