new_contents: from offset import go, maintask, run
  from offset.net import sock
  
  @maintask
  def main():
      fd = sock.bind_socket("tcp", ('127.0.0.1', 0))
      print(fd.name())
      while True:
          fd1 = fd.accept()
          print("accepted %s" % fd1.name())
          fd1.write(b"ok\n")
          fd1.close()
  
  run()
  
subject: add examples/test_polling.py