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Cannot get the function "OpenService" to return a valid handle

Posted on 2008-10-25
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Last Modified: 2013-12-04
Hi All,

I cannot get the OpenService function to return a valid file handle (returns 0).

Below is some code which illustrates the point and is self explanatory.

Any help with this would be greatly appreciated.

I am using Borland Delphi 2005 on a XP Professional SP2 PC.

Thanks in advance.

Ken.

var
  hdlOpenSCManager,
  hdlOpenService : SC_Handle;
  ServStat : TServiceStatus;
  dwStatus : DWORD;
begin
  dwStatus := DWORD (-1);

  hdlOpenSCManager := OpenSCManager (Nil, Nil, SC_MANAGER_ALL_ACCESS);

  if (hdlOpenSCManager > 0) then
    begin
      hdlOpenService := OpenService(hdlOpenSCManager, PChar('Windows Management Instrumentation'), SC_MANAGER_ALL_ACCESS);

  if hdlOpenService = 0 then
    ShowMessage(SysErrorMessage(GetLastError));

  // hdlOpenService always equals zero despite the fact the the service is both installed and running. Other services I have tested have given me the same result.

  // The error message is; "The specified service does not exist as an installed service"
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Question by:systemsgo
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1 Comment
 

Accepted Solution

by:
systemsgo earned 0 total points
ID: 22806352
Well, it appears that it isn't the display name of the service I should be using but the short version stored in the registry - well you learn something new everyday.

The working code is;

function ServiceGetStatus(sMachine, sService : string ) : DWORD;
var
  hdlOpenSCManager,
  hdlOpenService : SC_Handle;
  ServStat : TServiceStatus;
begin
  Result := DWORD (-1);

  hdlOpenSCManager := OpenSCManager(Nil, Nil, SC_MANAGER_ALL_ACCESS);

  if hdlOpenSCManager = 0 then
    exit;

  hdlOpenService := OpenService(hdlOpenSCManager, PChar(sService), SC_MANAGER_ALL_ACCESS);

  if hdlOpenService = 0 then
    begin
      CloseServiceHandle(hdlOpenSCManager);
      Exit;
    end;

  if QueryServiceStatus(hdlOpenService, ServStat) then
    Result := ServStat.dwCurrentState;

  CloseServiceHandle(hdlOpenService);
  CloseServiceHandle(hdlOpenScManager);
end;


So all the points go to me LOL.
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