WriteFile returning zero and GetLastError returning 997(ERROR_IO_PENDING)

[learningvisualc]

Hi all, I am trying to write to a port using CreateFile() and WriteFile() API's, but my WriteFile() is returning zero and on calling GetLastError() its returning error code 997 ERROR_IO_PENDING. I Know how to read a file when this happens but i am not getting how to write the file. Can anybody help me in doing this... Here is the code

serial_handle = CreateFile(port_arg, GENERIC_READ | GENERIC_WRITE,
0, NULL, OPEN_EXISTING,FILE_FLAG_OVERLAPPED,NULL);
success = WriteFile(serial_handle ,&temp,5,&temp1,&overlappRead);

I am not getting how to move ahead in this case Thanks in advance

[Cool_Dev]

WriteFile OVERLAPPED Structure See: If the function fails, or is completing asynchronously, the return value is zero (FALSE) NoteThe GetLastError code ERROR_IO_PENDING is not a failure; it designates the write operation is pending completion asynchronously. So your Write operation may be pending, so try checking 'Internal' member of OVERLAPPED structure or do Wait on its 'hEvent' member.

[Xequen]

If serial_handle was opened with FILE_FLAG_OVERLAPPED and lpOverlapped is not NULL, the write operation starts at the offset specified in the OVERLAPPED structure and WriteFile may return before the write operation has been completed. In this case, WriteFile returns FALSE and the GetLastError function returns ERROR_IO_PENDING. This allows the calling process to continue processing while the write operation is being completed. The event specified in the OVERLAPPED structure is set to the signaled state upon completion of the write operation. If serial_handle was not opened with FILE_FLAG_OVERLAPPED and lpOverlapped is NULL, the write operation starts at the current file position and WriteFile does not return until the operation has been completed. The former is asynchoronous and the latter is synchoronous. about your question,you can invoke "GetOverlappedResult( HANDLE hFile, // handle to file, pipe, or device LPOVERLAPPED lpOverlapped, // overlapped structure LPDWORD lpNumberOfBytesTransferred, // bytes transferred BOOL bWait // wait option );" this function to get result of WriteFile(); eg: success = WriteFil(serial_handle ,&temp,5,&temp1,&overlappRead); if(!success) { DWORD dwErrorCode = GetLastError(); switch(dwErrorCode) { case ERROR_IO_PENDING://IO is operating { GetOverlappedResult(serial_handle,&overlapped,&temp1,TRUE); //infinitely wait for WriteFile() operation compelete break; } //others error code default: { break } } }