WinComm/delphi/KPCOMM.md

TKPComm - Serial Communications Component

TKPComm is a non-visual Delphi 1.0 component providing serial port access via the Windows 3.1 comm API. It is a TComponent descendant that wraps OpenComm, ReadComm, WriteComm, and related functions into a property-driven interface. The application polls for received data; there is no event-driven notification infrastructure (no hidden window, no WM_COMMNOTIFY, no OnComm event).

Installs to the KP component palette tab.

Properties

Published (Design-Time and Runtime)

Property	Type	Default	Description
CommPort	Integer	1	Port number 1-16 (1=COM1, 2=COM2, etc.). Cannot be changed while port is open.
Settings	string	'9600,N,8,1'	Baud rate, parity, data bits, stop bits. Format: baud,parity,databits,stopbits. Can be changed while port is open to reconfigure on the fly.
PortOpen	Boolean	False	Opens or closes the serial port. Setting True calls OpenComm, BuildCommDCB, and SetCommState; False calls CloseComm.
InBufferSize	Integer	4096	Receive ring buffer size in bytes (minimum 64). Cannot be changed while port is open.
OutBufferSize	Integer	4096	Transmit ring buffer size in bytes (minimum 64). Cannot be changed while port is open.
Handshaking	THandshaking	hsNone	Flow control method (see below). Can be changed while port is open.
InputLen	Integer	0	Maximum bytes returned per Input read. 0 means up to 255 bytes.
InputMode	TInputMode	imText	Data reading mode. imBinary preserves embedded null bytes.
DTREnable	Boolean	True	Assert Data Terminal Ready when True. Toggled immediately if port is open.
RTSEnable	Boolean	True	Assert Request To Send when True. Toggled immediately if port is open.
NullDiscard	Boolean	False	Strip null bytes from received data.
EOFEnable	Boolean	False	Enable EOF character detection.
ParityReplace	string	'?'	Character substituted for parity errors. Empty string disables replacement.

Public (Runtime Only)

Property	Type	Access	Description
Input	string	Read	Reads available data from the receive buffer. Limited to 255 bytes per call (Delphi short string). Use ReadInputBuf for larger reads.
Output	string	Write	Writes data to the transmit buffer. Raises an exception if the port is not open or the write fails.
InBufferCount	Integer	Read	Bytes currently waiting in the receive buffer.
OutBufferCount	Integer	Read	Bytes currently waiting in the transmit buffer.
Break	Boolean	Read/Write	Asserts or clears the break signal via SetCommBreak/ClearCommBreak.

Methods

Public

Method	Description
Create(AOwner)	Constructor. Initializes defaults; FCommId set to -1 (closed).
Destroy	Destructor. Closes the port if still open.
ReadInputBuf(Buf, BufSize): Integer	Reads up to BufSize bytes into a caller-supplied PChar buffer. Returns the number of bytes actually read. Bypasses the 255-byte short string limit of the Input property.

Types

THandshaking

hsNone     No flow control
hsXonXoff  Software XON/XOFF (XON=$11, XOFF=$13)
hsRtsCts   Hardware RTS/CTS
hsBoth     Combined RTS/CTS and XON/XOFF

TInputMode

imText     Text mode (default)
imBinary   Binary mode (preserves embedded nulls)

DCB Flag Constants

Bit masks for the packed TDCB.Flags field:

Constant	Value	Description
dcbBinary	$0001	Binary mode (always set)
dcbRtsDisable	$0002	RTS disabled
dcbParity	$0004	Parity check/replacement
dcbOutxCtsFlow	$0008	CTS output flow control
dcbOutxDsrFlow	$0010	DSR output flow control
dcbDtrDisable	$0020	DTR disabled
dcbOutX	$0040	XON/XOFF output flow control
dcbInX	$0080	XON/XOFF input flow control
dcbPeChar	$0100	Parity error character replacement
dcbNull	$0200	Null byte stripping
dcbChEvt	$0400	Character event notification
dcbDtrflow	$0800	DTR flow control
dcbRtsflow	$1000	RTS flow control

Port Lifecycle

1. Create the component and set properties (CommPort, Settings, buffer sizes, Handshaking, etc.).
2. Set PortOpen := True. This calls OpenComm, builds the DCB from the Settings string, applies flow control, null discard, parity replace, and asserts DTR/RTS.
3. Poll Input or call ReadInputBuf in the application's main loop. Set Output to send data.
4. Set PortOpen := False to close. DTR and RTS are cleared, break is released, and CloseComm is called.
5. The destructor closes the port automatically if still open.

Usage Example

FComm := TKPComm.Create(Self);
FComm.CommPort := 1;
FComm.Settings := '115200,N,8,1';
FComm.PortOpen := True;

{ In the main loop: }
Len := FComm.ReadInputBuf(@Buf, SizeOf(Buf));
if Len > 0 then
  ProcessData(@Buf, Len);

{ To send data: }
FComm.Output := 'AT' + #13;

Platform Notes

• Targets Windows 3.1 using the 16-bit comm API (OpenComm, ReadComm, WriteComm, GetCommState, SetCommState, GetCommError, EscapeCommFunction, BuildCommDCB).
• No notification infrastructure. The application must poll for data. There is no hidden window, no WM_COMMNOTIFY handling, and EnableCommNotification is not used.
• The Input property is limited to 255 bytes by Delphi 1.0's short string type. Use ReadInputBuf for bulk reads (2048+ bytes per call).
• EscapeCommFunction returns 0 on success in the 16-bit API (opposite of the Win32 convention).
• Uses { } comments (Delphi 1.0 does not support // comments).