// 等待一条AT命令执行结果

function TCnModem.WaitATResult(Delay: Cardinal): string;

var

  Tick: Cardinal;

begin

  FWaitATResult := True;

  try

    FATResult := '';

    Tick := GetTickCount;

    while (GetTickCount - Tick < Delay) and (FATResult = '') do

      Application.HandleMessage;

    Result := FATResult;

    FATResult := '';

  finally

    FWaitATResult := False;

  end;

end;



// 发送一条AT命令，返回是否成功

function TCnModem.SendATOk(AT: string; Delay: Cardinal): Boolean;

var

  i, j: Integer;

  s: string;

begin

  Result := False;

  for i := 0 to 2 do

  begin

    WriteATCommand(AT);

    for j := 0 to 2 do

    begin

      s := Trim(UpperCase(WaitATResult(Delay)));

      if Pos('OK', s) > 0 then

      begin

        Result := True;

        Exit;

      end

      else if Pos('ERROR', s) > 0 then

      begin

        InvalidCommand(AT);

        Exit;

      end;

    end;

  end;

end;



// 接收到数据

procedure TCnModem.ReceiveData(Buffer: PAnsiChar; BufferLength: WORD);

var

  s: AnsiString;

begin

  if FWaitATResult then       // 正在等待AT命令执行结果

  begin

    FATResult := {$IFDEF DELPHI12_UP}String{$ENDIF}(Buffer);

    Exit;

  end;

  s := Buffer;

  s := {$IFDEF DELPHI12_UP}AnsiString{$ENDIF}(Trim(UpperCase({$IFDEF DELPHI12_UP}String{$ENDIF}(s))));

  if (ModemState in [msOffline, msOnlineCommand, msConnecting]) and (s = 'RING') then

    Ring                      // 振铃信号

  else if (ModemState = msOnline) and (s = 'NO CARRIER') then

    DisConnect                // 载波丢失

  else

    inherited;

end;