| 摘要 |
PROBLEM TO BE SOLVED: To retransmit status change data whose transmission has failed due to circuit disconnection, etc. SOLUTION: An Ethernet driver 10 detects the change of data, prepares status change data 11, stores the status change data 11 into a status change data storing means 12 and also makes a transmission request (a) for the status change data 11 to an Ethernet I/F 20. The I/F 20 transmits the status change data 11 to an opposite device 30 according to the request (a). If response does not arrive even though the I/F 20 performs retransmissions b1 and b2, the I/F 20 notifies the driver 10 of a transmission failure (e) and also notifies (f) the device 30 of the cutoff of connection. The device 30 requests (g) reconnection to the I/F 20. The I/F 2 notifies (h) the device 30 of reconnection permission and completes line reconnection of an Ethernet TCP protocol. If the driver 10 is notified (e) of the transmission failure, the driver 10 reads status change data 13 (=11) to be retransmitted from the status change data storing means 12 after the completion of the line reconnection, and makes a transmission request (i) for the status change data 13 to the I/F 20. Since the status change data are stored in the storing means 12, a retransmission request (i) is possible.
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