docs: def get_free_udp_port():
      '''
      Get a free UDP port.
  
      Note this is vlunerable to race conditions.
      '''
      import socket
      sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
      sock.bind(('localhost', 0))
      addr = sock.getsockname()
      sock.close()
      return addr[1]