windows ReadFile() doesn'r return until reading sizeToRead value.

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In serial communication, ReadFile doesn't return until reading as many as sizeToRead parameter.

It is so weird, because actually until yesterday, it works normally with same code, same laptop, returning though it doesn't receive as many as sizeToRead but any bytes.

But today my code show weird symptom like this.

serialHandle = CreateFile(L"\\\\.\\COM1",
    GENERIC_READ | GENERIC_WRITE,
    0,
    0,
    OPEN_EXISTING,
    FILE_ATTRIBUTE_NORMAL,
    0);

DCB serialInfo = {0};

GetCommState(serialHandle, &serialInfo)

serialInfo.DCBlength = sizeof(DCB);
serialInfo.BaudRate = CBR_19200;
serialInfo.fBinary = TRUE;
serialInfo.fParity = TRUE;          
serialInfo.fErrorChar = TRUE;
serialInfo.fNull = TRUE;
serialInfo.fAbortOnError = FALSE;   //TODO
serialInfo.ByteSize = 8;
serialInfo.Parity = SPACEPARITY;
serialInfo.StopBits = ONESTOPBIT;
serialInfo.ErrorChar = 0xFF;    

SetCommState(serialHandle, &serialInfo

ReadFile(serialHandle, buffer, numberOfBytesToRead, &numOfBytesRead, NULL)

numberOfBytesToRead is 256, So ReadFile return after getting 256 bytes

asked 58 secs ago

asleea

120

windows ReadFile() doesn'r return until reading sizeToRead value.