I don't want to use a hard-coded port number, I want it to bind to
INADDR_ANY with a port of zero. The system will select a free port.

Then, I can advertise that port using mDNS/DNS-SD.

Is this possible? I can maybe set :Port to 0, but I am searching the
webrick src and can't see a way to get the underlying socket up, so I
can ask it it's port.

My next try will be looping until I register a free port, but that's an
ugly, ugly solution!

Cheers,
Sam