SetupComm

Overview

Group

Quick Info

Windows NT
Yes
Win95
Yes
Win32s
No
Import Library
kernel32.lib
Header File
winbase.h
Unicode
No
Platform Notes
None

The SetupComm function initializes the communications parameters for a specified communications device.

BOOL SetupComm(

HANDLE hFile,	// handle of communications device
DWORD dwInQueue,	// size of input buffer
DWORD dwOutQueue	// size of output buffer
);

Parameters
hFile

Identifies the communications device. The CreateFile function returns this handle.

dwInQueue

Specifies the recommended size, in bytes, of the device's internal input buffer.

dwOutQueue

Specifies the recommended size, in bytes, of the device's internal output buffer.

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
After a process uses the CreateFile function to open a handle to a communications device, it can call SetupComm to set the communications parameters for the device. If it does not set them, the device uses the default parameters when the first call to another communications function occurs.

The dwInQueue and dwOutQueue parameters specify the recommended sizes for the internal buffers used by the driver for the specified device. For example, YMODEM protocol packets are slightly larger than 1024 bytes. Therefore, a recommended buffer size might be 1200 bytes for YMODEM communications. For Ethernet-based communications, a recommended buffer size might be 1600 bytes, which is slightly larger than a single Ethernet frame.

The device driver receives the recommended buffer sizes, but is free to use any input and output (I/O) buffering scheme, as long as it provides reasonable performance and data is not lost due to overrun (except under extreme circumstances). For example, the function can succeed even though the driver does not allocate a buffer, as long as some other portion of the operating system provides equivalent functionality.

If the device driver determines that the recommended buffer sizes involve transfers beyond its ability to handle, the function can fail.