The backward technology in DTU protocol exists the problems of poor stability, low data security, heavy loader of database and difficulty to maintain and develop the software of DSC and clients. This paper analyzes the characteristics of communication between DTU and DSC, adopts the method of the registration packet and heartbeat bag together, and designs a closed-loop two-ring-opening operation mode among the communication protocol. The result shows that this design improved the reliability of the communication, reduces the development difficulty of DSC and client management software, and reaches the design requirements.