procedure TComRead.Execute;
var
ComStat: TComStat;
dwMask, dwError: DWORD;
OverRead: TOverlapped;
Buf: array[0..20] of char;
dwRead: DWORD;
dd: string;
begin
FreeOnTerminate := True;
while not Terminated do
begin
dwMask:=0;
WaitCommEvent(CId, dwMask, @OverRead);
if dwMask = EV_RXCHAR then
begin
ClearCommError(CId, dwError, @ComStat);
dwRead := ComStat.cbInQue;
if dwRead > 0 then
begin
ReadFile(CId, Buf, dwRead, dwRead, @OverRead);
Form2.Panel1.Caption:=string(Buf);
end;
end; {while}
end;
end;

procedure TReadThread.Execute;
var
ComStat: TComStat;
dwMask, dwError: DWORD;
OverRead: TOverlapped;
Buf: array[0..$FF] of Byte;
dwRead: DWORD;
begin
OverRead.hEvent := CreateEvent(nil, True, False, nil);
if OverRead.hEvent = Null then
raise Exception.Create('Error creating read event');

FreeOnTerminate := True;

while not Terminated do
begin
if not WaitCommEvent(cId, dwMask, @OverRead) then
begin
if GetLastError = ERROR_IO_PENDING then
WaitForSingleObject(OverRead.hEvent, INFINITE)
else
raise Exception.Create('Error waiting port event');
end;

if not ClearCommError(cId, dwError, @ComStat) then
raise Exception.Create('Error clearing port');

dwRead := ComStat.cbInQue;

if dwRead > 0 then
begin
if not ReadFile(cId, Buf, dwRead, dwRead, @OverRead) then
raise Exception.Create('Error reading port');
// В Buf находятся прочитанные байты
// Далее идет обработка принятых байтов
end;
end;
end;

cId:= CreateFile(‘COM1’, GENERIC_READ or GENERIC_WRITE, 0, nil,
OPEN_EXISTING, FILE_FLAG_OVERLAPPED, 0);
if cId= INVALID_HANDLE_VALUE then
raise Exception.Create('Error opening port');

if not GetCommState(cId, Dcb) then
raise Exception.Create('Error setting port state');

Dcb.BaudRate := CBR_9600;
Dcb.Parity := NOPARITY;
Dcb.ByteSize := 8;
Dcb.StopBits := ONESTOPBIT;

if not SetCommState(cId, Dcb) then
raise Exception.Create('Error setting port state');
if not PurgeComm(cId, PURGE_TXCLEAR or PURGE_RXCLEAR) then
raise Exception.Create('Error purging port');