C/S soekct programming problems. Why is the c client still in the connection status when the S client prompts that C has been disconnected?

I used the socket control that comes with D6 and made a C/SProgram. C sends image data to the S end and adds the method that can be reconnected after a network error occurs. After the connection starts, the image data can be normally transmitted to the S end. In addition, after manual disconnection (for example, the send is closed, the IP address is modified, or the IP address is dropped), it can be automatically connected. But 5 to 10 hours later (the time is not fixed ). The connection between C and S is faulty. The C-end is disconnected (the S-end has a display function), and the C-end has no response. Therefore, the C end also thinks that it is in the connection status. But that's strange. Is C disconnected during event processing on the send? Restart the C-end and run properly again!
I thought it was a control problem and changed the idtcpclient and idtcpserver controls of Indy. The results also show up-after a period of normal operation. It will no longer be passed in. The S end also prompts that the C end has been disconnected. The C end has stopped.
Later, two sets of controls were used to test the connection between C and S, and the other was to send image data. The problem persists.
Can someone help me. I have used many methods to solve this problem? In principle, the send prompts disconnection. The C end should also be disconnected.

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