大家看看下面的代码？

Question

procedure TForm1.Button1Click(Sender: TObject);
var
  hCom:THandle;
  Timeout:TCommTimeouts;
  Dataout,Datain:pchar;
  Overlapped:POverlapped;
  BufferSize:DWORD;
begin
  hcom:=CreateFile('Com3',
    GENERIC_READ or GENERIC_WRITE,
                    0,
                    nil,
                    OPEN_EXISTING,
                    FILE_ATTRIBUTE_NORMAL or FILE_FLAG_OVERLAPPED,
                    0);
  Timeout.ReadIntervalTimeout:=10;
  Timeout.ReadTotalTimeoutMultiplier:=20;
  Timeout.ReadTotalTimeoutConstant:=30;
  SetCommTimeouts(hCom,Timeout);
  SetEvent(hCom);  Dataout:='S';
  GetMem(overlapped,sizeof(TOverlapped));
  BufferSize:=4096;
  GetMem(Datain,4096); if WriteFile(hCom,Dataout,1,BufferSize,Overlapped) then
    showmessage('Write Right');
  if ReadFile(hCom,Datain,1,BufferSize,Overlapped) then
    showmessage('Read Right');  //showmessage(string(Datain));  FreeMem(Datain);
  FreeMem(Overlapped);
  Closehandle(hCom);
end;上面的代码应该是发送一字符，读取一个字符，上面的代码能否正确执行，得到想要的结果，这个代码我找来的。

Answer 1

就是，Datain算什么东西，接收上来的码？，不管Dataout为多少它的值都一样
showmessage(string(Datain));
不知道这样发送接接收对不对啊。哪位有人帮忙看看

Answer 2

http://expert.csdn.net/Expert/topic/1669/1669798.xml?temp=.5736963
一样的错吧
WriteFile(hCom,Dataout^,1,BufferSize,Overlapped)

Answer 3

不是啊，我的是串口问题，用的是API函数WriteFile和ReadFile，而你给的是Delphi本身的函数FileRead，应该不是这个原因吧。

Answer 4

好多问题：
1 串口没有设置SetCommState，PurgeComm，SetupComm，SetCommTimeouts
2 没有设置WriteTotalTimeOutXXX，且ReadTotalTimeoutConstant太小
3 TOverlapped没有清0
4 没有检查WriteFile和ReadFile的返回值，返回False时要用GetOverlappedResult获得实际读写的字节数，如果等于要读写的字节数，也要认为成功

Answer 5

好不容易才找到一个N年前些的控件，给你参考参考，分可不能少 :)unit SNCOMM;interfaceuses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs;type
  TSNCOMM = class(TComponent)
  private
    { Private declarations }
    FPortName:   String;
    FComHandle: THandle;
  protected
    { Protected declarations }
  public
    { Public declarations }
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
    function Connect(ComPort: Byte; bps: Cardinal): Boolean;
    procedure Disconnect;
    function Read(var Buff; Bytes: Cardinal): Cardinal;
    function Write(var Buff; Bytes: Cardinal): Cardinal;
    function ReadByte(var B: Byte): Boolean;
    function SendByte(B: Byte): Boolean;
    function WriteByte(B: Byte): Boolean;
    procedure Clear;
    function BytesNeedRead: Cardinal;
    function Connected: Boolean;
    procedure FlushBuffers(Rx,Tx: Boolean);    property PortName: String read FPortName;
  published
    { Published declarations }
  end;procedure Register;implementationprocedure Register;
begin
  RegisterComponents('Standard', [TSNCOMM]);
end;{ TSNCOMM }function TSNCOMM.BytesNeedRead: Cardinal;
var
  err: Cardinal;
  cs: TCOMSTAT;
begin
  Result := 0;
  if not Connected then Exit;
  if not ClearCommError(FComHandle,err,@cs) then Exit;
  Result := cs.cbInQue;
end;procedure TSNCOMM.Clear;
begin
  if not Connected then Exit;
  PurgeComm(FComHandle,PURGE_TXABORT or PURGE_RXABORT or PURGE_TXCLEAR or PURGE_RXCLEAR);
end;function TSNCOMM.Connect(ComPort: Byte; bps: Cardinal): Boolean;
var
  dcb: TDCB;
  tos: TCOMMTIMEOUTS;
  n: Cardinal;
begin
  Result := False;
  if Connected then Exit;  case bps of
    110:    n := CBR_110;
    300:    n := CBR_300;
    600:    n := CBR_600;
    1200:   n := CBR_1200;
    2400:   n := CBR_2400;
    4800:   n := CBR_4800;
    9600:   n := CBR_9600;
    14400:  n := CBR_14400;
    19200:  n := CBR_19200;
    38400:  n := CBR_38400;
    56000:  n := CBR_56000;
    57600:  n := CBR_57600;
    115200: n := CBR_115200;
    128000: n := CBR_128000;
    256000: n := CBR_256000;
    else    Exit;
  end;  FPortName := Format('COM%d',[ComPort]);
  FComHandle := CreateFile( PChar(FPortName),
                            GENERIC_READ or GENERIC_WRITE,
                            0, // Not shared
                            nil, // No security attributes
                            OPEN_EXISTING,
                            FILE_ATTRIBUTE_NORMAL or FILE_FLAG_OVERLAPPED,
                            0 // No template
                          ) ;
  if Connected then
  begin
    FillChar( dcb, SizeOf(dcb), 0 );
    dcb.DCBLength := sizeof(dcb);
    dcb.BaudRate := n;
    dcb.Flags := 1; { binary mode }
    dcb.ByteSize := 8;
    dcb.Parity := 0;
    dcb.StopBits := 0;    tos.ReadIntervalTimeout := 100;
    tos.ReadTotalTimeoutMultiplier := 100;
    tos.ReadTotalTimeoutConstant := 1000;
    tos.WriteTotalTimeoutMultiplier := 100;
    tos.WriteTotalTimeoutConstant := 1000;    Result := True;    if SetCommState( FComHandle, dcb )
       and PurgeComm( FComHandle, PURGE_TXABORT or PURGE_TXCLEAR or PURGE_RXABORT or PURGE_RXCLEAR )
       and SetupComm( FComHandle, 100, 100 )
       and SetCommTimeouts( FComHandle, tos )
       then Exit;    Disconnect;
    Result := False;
  end;  FPortName := '';
end;function TSNCOMM.Connected: Boolean;
begin
  Result := FComHandle <> INVALID_HANDLE_VALUE;
end;constructor TSNCOMM.Create(AOwner: TComponent);
begin
  inherited;
  FComHandle := INVALID_HANDLE_VALUE;
end;destructor TSNCOMM.Destroy;
begin
  Disconnect;
  inherited;
end;procedure TSNCOMM.Disconnect;
begin
  if Connected then
  begin
    CloseHandle(FComHandle);
    FComHandle := INVALID_HANDLE_VALUE;
  end;
end;procedure TSNCOMM.FlushBuffers(Rx, Tx: Boolean);
var
  Flag: Cardinal;
begin
  if not Connected then Exit;
  Flag := 0;
  if Rx then Flag := Flag or PURGE_RXABORT or PURGE_RXCLEAR;
  if Tx then Flag := Flag or PURGE_TXABORT or PURGE_TXCLEAR;
  if Flag <> 0 then PurgeComm(FComHandle,Flag);
end;function TSNCOMM.Read(var Buff; Bytes: Cardinal): Cardinal;
var
  ol: TOVERLAPPED;
begin
  Result := 0;
  if not Connected then Exit;  FillChar(ol,SizeOf(ol),0);
  if not ReadFile(FComHandle,Buff,Bytes,Result,@ol) then
    GetOverlappedResult(FComHandle,ol,Result,True);
end;function TSNCOMM.ReadByte(var B: Byte): Boolean;
begin
  Result := Read(B,1) = 1;
end;function TSNCOMM.SendByte(B: Byte): Boolean;
begin
  Result := Write(B,1) = 1;
end;function TSNCOMM.Write(var Buff; Bytes: Cardinal): Cardinal;
var
  ol: TOVERLAPPED;
begin
  Result := 0;
  if not Connected then Exit;  FillChar(ol,SizeOf(ol),0);
  if not WriteFile(FComHandle,Buff,Bytes,Result,@ol) then
    GetOverlappedResult(FComHandle,ol,Result,True);
end;function TSNCOMM.WriteByte(B: Byte): Boolean;
begin
  Result := Write(B,1) = 1;
end;end.

Answer 6

这不是串口通信，一顿API函数么，估计上面代码不能执行，写的太简单了，好象缺点什么东西
我看小查说的不错