CallNamedPipe

The CallNamedPipe function connects to a message-type pipe (and waits if an instance of the pipe is not available), writes to and reads from the pipe, and then closes the pipe.

BOOL CallNamedPipe(

LPCTSTR lpNamedPipeName,	// pointer to pipe name
LPVOID lpInBuffer,	// pointer to write buffer
DWORD nInBufferSize,	// size, in bytes, of write buffer
LPVOID lpOutBuffer,	// pointer to read buffer
DWORD nOutBufferSize,	// size, in bytes, of read buffer
LPDWORD lpBytesRead,	// pointer to number of bytes read
DWORD nTimeOut	// time-out time, in milliseconds
);

Parameters

lpNamedPipeName

Pointer to a null-terminated string specifying the pipe name.

lpInBuffer

Pointer to the buffer containing the data written to the pipe.

nInBufferSize

Specifies the size, in bytes, of the write buffer.

lpOutBuffer

Pointer to the buffer that receives the data read from the pipe.

nOutBufferSize

Specifies the size, in bytes, of the read buffer.

lpBytesRead

Pointer to a 32-bit variable that receives the number of bytes read from the pipe.

nTimeOut

Specifies the number of milliseconds to wait for the named pipe to be available. In addition to numeric values, the following special values can be specified:

Value	Meaning
NMPWAIT_NOWAIT	Does not wait for the named pipe. If the named pipe is not available, the function returns an error.
NMPWAIT_WAIT_FOREVER	Waits indefinitely.
NMPWAIT_USE_DEFAULT_WAIT	Uses the default time-out specified in a call to the CreateNamedPipe function.

Return Values

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended error information, call GetLastError.

Remarks

Calling CallNamedPipe is equivalent to calling the CreateFile (or WaitNamedPipe, if CreateFile cannot open the pipe immediately), TransactNamedPipe, and CloseHandle functions. CreateFile is called with an access flag of GENERIC_READ | GENERIC_WRITE, an inherit handle flag of FALSE, and a share mode of zero (indicating no sharing of this pipe instance).

If the message written to the pipe by the server process is longer than nOutBufferSize, CallNamedPipe returns FALSE, and GetLastError returns ERROR_MORE_DATA. The remainder of the message is discarded, because CallNamedPipe closes the handle to the pipe before returning.

CallNamedPipe fails if the pipe is a byte-type pipe.

See Also

CloseHandle, CreateFile, CreateNamedPipe, TransactNamedPipe, WaitNamedPipe

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