Question

When I try to connect to the COM port on Windows 7, using AsyncPro (TApdComPort), I’m getting the error message like “Device already open”. But the same application working fine in Win Xp machine. I’m used Delphi 6 to develop the program. Please help me to resolve this issue.
Appreciate your help.
Thanks.

Answer 1

What component are you using to connect to the COM Port?

If you are using CreateFile API to open the port use GetLastError() API for a detalied error of your problem.

If that doesn’t help you it means it’s a hardware problem

Don’t know about the component you are using ApdComPort but you could do a simple test write a simple application to open the port just like this

var
  comHandle : THandle;
begin
  comHandle := CreateFile('COM66',GENERIC_READ or GENERIC_WRITE,0,nil,OPEN_EXISTING,0,0);
  if comHandle = INVALID_HANDLE_VALUE then ShowMessage(SysErrorMessage(GetLastError))
  else ShowMessage('Port opened');
end //Make shure to replace COM66 with your actual COM Port you wish to open

If it shows Port opened then it’s a problem with the component you are using so i would recommend this one http://sourceforge.net/projects/comport/ post here other error message to find a solution.