VIP33: Socket.* CLI commands

socket.open
  Attempts to open all configured incoming sockets (= -a arguments)
  Success if they all open
  Failure if any fail to open, all sockets left closed.
  This will remain be the behavior without arguments, when optional arguments are defined.

socket.close
  Closes all configured incoming sockets
  Always success.
  This will remain be the behavior without arguments, when optional arguments are defined.

socket.listen
  Output:
     name state fd bound_address a_arg_possibly_filtered_by_transport

  for instance when open:
     a0 open 8 0.0.0.0:3939 :0,PROXY
     a0 open 9 [::]:4029 :0,PROXY

  example when closed:
     a0 closed - - :0,PROXY