Disconnect Ethernet cable my program crach

im using wiz5500se2 board with my code. Im using loopback program from example. Its work correctly. But if im disconnect ethernet cable manualy tcp program is waiting PHYStatus_Check after connected ethernet cable led is work but socket connection is not working. i give win error 10061 or 10062 . When im resetting my board program is working.
Second question how can i use watchdog

In TCP communication, if there is no response for a certain time, a timeout occurs and the connection is lost. How long have you unplugged the ethernet cable? You can delay the timeout by modifying the firmware.

And we not provide watchdog code. you can add watchdog code in to this project(GitHub - Wiznet/WIZ550S2E: Serial to Ethernet Module based on W5500 & Cortex-M0).

Error 10061 indicates no connection could be made because the target computer actively refused it. The most common cause is a misconfigured server, full server, firewall issue or incorrect Port specified by the client.