type
TWTSQuerySessionInformationA = function(hServer: THandle; SessionId: DWORD; WTSInfoClass: _WTS_INFO_CLASS; var ppBuffer: Pointer; var pBytesReturned: DWORD): BOOL; stdcall;

const WTS_CURRENT_SESSION = DWORD(-1);
var ppBuffer: Pointer;
pBytesReturned: DWORD
begin
    _TWTSQuerySessionInformationA := GetProcAddress(LoadLibrary(PAnsiChar('wtsapi32.dll')), PAnsiChar('WTSQuerySessionInformationA'));
    Result := TWTSQuerySessionInformationA(_TWTSQuerySessionInformationA)(WTS_CURRENT_SERVER_HANDLE, WTS_CURRENT_SESSION, WTSClientName, ppBuffer, pBytesReturned);
    try
        if not Result then
            RaiseLastOSError;
    except
    end;
end;