code: async def connect(self):
          
          self.reader, self.writer = await asyncio.open_connection(
              host=self.hostname,
              port=self.port,
              loop=self.loop)
          self.closed = False
          self._response_task = asyncio.ensure_future(self._response_handler())
          query = {
              "MPRPC": self.VERSION,
              "AUTH": {
                  "USERNAME": self.username,
                  "PASSWORD": self.password
              }
          }
          queryb = self.encoder(query)
          if self.debug is True:
              print("send auth {}".format(queryb))
          self.writer.write(queryb)
          self._login_fut = self.loop.create_future()
          self.remote_info = await self._login_fut
          if self.remote_info is False:
              raise abort(501)
          if self.heart_beat:
              self._heartbeat_task = asyncio.ensure_future(
                  self._heartbeat_callback())
docs: 与远端建立连接.
  
          主要执行的操作有:
          + 将监听响应的协程_response_handler放入事件循环
          + 如果有验证信息则发送验证信息
          + 获取连接建立的返回