lpNumberOfBytesSent

lpNumberOfBytesSent is a parameter used in Microsoft Windows API functions, primarily related to network communication. It is a pointer to a DWORD variable that receives the total number of bytes successfully sent by the function. This parameter is typically output-only, meaning the function writes data into the memory location pointed to by lpNumberOfBytesSent, rather than reading data from it. When a Windows API function that sends data over a network or to a device completes its operation, it will update the value at the address specified by lpNumberOfBytesSent with the count of bytes that were transmitted. This information is crucial for applications to track the progress of data transmission and to ensure that all intended data has been sent. For example, functions like `send` or `WSASend` in the Winsock API use lpNumberOfBytesSent to report how much data was actually transmitted in a single call. Developers can then use this value to determine if the entire message was sent, or if further transmission is required. It is important for the calling application to allocate sufficient memory for the DWORD variable that lpNumberOfBytesSent points to.