Settings → Network makes a key, shown once and stored encrypted; the api sends
it to the probe as a Bearer token, and a new probe address drops it. A probe
with PROBE_KEY only answers that key. Without one it stays open, and
Diagnostics strongly recommends setting it.
The server checks itself (public IP, DNS, local networks, phone ACL, SIP transports, free audio
ports) and says how to fix each problem. A quick or complete network test asks the probe
(apps/probe, own image) to test this server from outside: HTTP/HTTPS, SIP over UDP/TCP/TLS, the
browser phone's /ws, sampled audio ports. The probe only tests the address that asks.
The audio port range comes from RTP_PORT_START/END (default 10000-20000).
iamdoubz