Initializes the communications parameters for a specified communications device.

BOOLEAN SetupComm(
  COMMHANDLE hComm,     // handle to communications device
  DWORD dwInQueue,      // size of input buffer
  DWORD dwOutQueue      // size of output buffer
);

Parameters

hComm

[in] Handle to the communications device. OpenCommn returns this handle.

dwInQueue

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

dwOutQueue

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

Return Values

Non-zero

Success.

0 (zero)

Failure. To determine the status, call GetLastRtError.

Status

E_BUSY

An I/O operation is already in progress.

E_DISCONNECTED

COMM channel is closed.

E_PARAM

Invalid parameter.

Remarks

After a process uses OpenComm 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 system provides equivalent functionality.

Requirements