The PortIO95 Parallel Port Interface

Error Messages and Codes

All communication to the PortIO95 VxD is done through the Windows 95 DeviceIoControl() function call. If the DeviceIoControl call is not successful it will return a value of 0 (non zero is returned for success). After an unsuccessful call further information on the cause of the error can be obtained through a second call to the function GetLastError(). For Visual C++ Version 4.0 it could be issued as:

The value returned by GetLastError() will be a number. This number can be used to look up the error message in the table below:

Return Codes


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