Microsoft Docs

Winsock Error Handling

Understanding and handling errors is crucial for developing robust Winsock applications. Winsock functions return specific error codes to indicate the cause of a failure.

Retrieving Error Codes

The primary way to retrieve a Winsock error code is by calling the WSAGetLastError function after a Winsock function returns a failure. This function returns the most recent error code for the calling thread.

int error = WSAGetLastError();

Common Winsock Error Codes

The following table lists some of the most common Winsock error codes and their meanings:

Handling Specific Errors

When an error occurs, your application should check the return value of WSAGetLastError and take appropriate action. For example, if you encounter WSAEWOULDBLOCK on a non-blocking socket, you might retry the operation later.

if (bytesSent == SOCKET_ERROR) {
    int error = WSAGetLastError();
    if (error == WSAEWOULDBLOCK) {
        // Handle non-blocking send failure, maybe queue the data
        printf("Send would block. Retrying later...\n");
    } else {
        // Handle other send errors
        fprintf(stderr, "Send failed with error: %d\n", error);
    }
}

Best Practices

• Always call WSAGetLastError immediately after a Winsock function returns a failure.
• Use symbolic constants (e.g., WSAEWOULDBLOCK) instead of raw error codes for better code readability and maintainability.
• Implement error handling strategies appropriate for the specific error codes encountered.
• Consider using event notification mechanisms (like WSAEventSelect or overlapped I/O) to manage socket operations and avoid blocking.