Open the 4200 client, enter the control panel-device management, select the device to view the device network status, as shown in the following figure:

HCNetSDK.dll[1]: The user name or password is incorrect. You can delete the device, restart the device after power off, add it to the client again, and enter the exact user name and password of the device;

Add device error prompt HCNetSDK.dll[7]: The device is offline or connection timeout caused by the network. If it is a local area network device, you can delete the device, check the device IP, and test whether it can ping the computer; if it is a domain name or external network IP, you can test whether the port mapping works on the computer. ("How to obtain the computer's IP address, how to ping the device's IP, how to execute a long ping command, how to ping a large packet, how to test whether the port is connected" can be obtained through the official account chat window search~)