import socket

def get_open_port():
  """ Retrieves an open port on the system. """

  # Bind a socket to a random port. We can then ask for the port number,
  # and return it.
  s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
  s.bind(("", 0))
  s.listen(1)
  port = s.getsockname()[1]
  s.close()

  return port