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This allows NetListen to be done before other intialization, so that
listening sockets for peers are created already. This makes
orchestration a lot easier. E.g. listener proxy will have listening
sockets for peers already created when still waiting for connector proxy
to connect.

Preparation to add additional proxy implementations.

Uses a TCP socket to exchange connection info.

With this longer tests (5sec iperf with kvm) work without problems now.