text: from __future__ import print_function
  from __future__ import absolute_import
  from time import sleep
  
  from vnpy.rpc import RpcClient
  
  
  class TestClient(RpcClient):
      """
      Test RpcClient
      """
  
      def __init__(self):
          """
          Constructor
          """
          super(TestClient, self).__init__()
  
      def callback(self, topic, data):
          """
          Realize callable function
          """
          print(f"client received topic:{topic}, data:{data}")
  
  
  if __name__ == "__main__":
      req_address = "tcp://127.0.0.1:2014"
      sub_address = "tcp://127.0.0.1:4102"
  
      tc = TestClient()
      tc.subscribe_topic("")
      tc.start(req_address, sub_address)
  
      while 1:
          print(tc.add(1, 3))
          sleep(2)
  