Port 0 asks msquic for an ephemeral port, but nothing read that port
back, so a QUIC server had to pick a fixed one and hope nothing else held
it, and this suite has to hand every QUIC test a port of its own.
ListenerStart writes the port of the UDP socket it bound into the
listener's local address; the constructor now reads it with
QUIC_PARAM_LISTENER_LOCAL_ADDRESS right after the start, and Port()
returns it. It is valid as soon as the constructor returns and still
after Stop(), and 0 on a moved-from listener. ListenerTCP has had the
same since d6f8f4e.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Jorijn van der Graaf
7dace8bb03