pub(crate) fn open(ipv6: bool) -> Result<(TcpListener, String), SyncError>Expand description
Opens the door: 127.0.0.1 on a port the system chooses; else, when
ipv6 allows it, [::1] (Google takes either; Microsoft takes no IPv6
loopback). The listener, and the redirect address the provider is given
(no path: http://127.0.0.1:<port>).