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