The main process of Hikvision SDK interface calling follows a standardized procedure to ensure stable and secure device communication.

First, initialization is performed. The NET_DVR_Init function is called to initialize the SDK operating environment, and parameters such as connection timeout and reconnection can be configured. Subsequently, device registration and login are carried out. Functions such as NET_DVR_Login_V40 are used to obtain a unique user ID through the device IP address, port, username, and password, which serves as the credential for all subsequent operations.

After successful login, specific functional interfaces can be invoked as required. For example, NET_DVR_RealPlay_V40 is used to start real-time preview, or NET_DVR_DownloadByTime is called for video playback and download. During this process, the SDK typically returns data streams or status information to the application via callback functions or asynchronous messages.

Finally, cleanup and logout must be executed before the program exits. Call NET_DVR_Logout to log out the connected device, and invoke NET_DVR_Cleanup to release all resources occupied by the SDK. This is a critical step to prevent memory leaks.

The entire process must strictly follow the calling sequence specified in the SDK manual and handle exceptions properly to ensure the robustness of the program.