Abstract: This specification discloses a transmission system, device and method that prevent data loss. The invention uses a first channel and a second channel to send same packet encapsulating same target data to a receiving end. After confirming the reception of the packet, the receiving end drops the duplicated packet. The receiving end only processes yet processed packet. This technique can reduce the chances of losing data.

Abstract: This specification discloses a communication system across networks and the method thereof for processing remote controls of devices in a private network from a public network. By providing a server end that contains correspondence relations between client ends and mobile ends in a public network, packets in the public network are automatically transmitted to devices in a private network according to the correspondence table in the server end for remote controls. The invention increases the convenience in managing devices in a private network.

Abstract: For use in a dual-path network system comprising a master end, a main transmission path, a sub-transmission path, an intermediary device, and a slave end, a network redundancy check application program management method is disclosed to virtualize COM ports of multiple IP addresses in the master end into one single virtualized COM port by means of a driver in the master end so that the user/user's application program needs only to manage/monitor the virtualized COM port. Through the driver and the firmware formed in the intermediary device, the invention covers all operation modes, and the user/user's application program needs not to worry about system complication resulted from the redundancy check system. Under the network architecture of the present invention, the master end enjoys the high stability of dual-path, and the manager needs not to manage a big number of COM ports.