Hi, I have a big problem.
I have a service that monitors sessions on a PC/Server.
If I develop the application in 32 bit and it works, but if I develop the application in 64 bit it goes into error (but not always!!):
Error 87 : The Parameter is incorrect This is my code:   Unit Wtsapi32: unit UN_Wtsapi32; interface uses Windows; const WINSTATIONNAME_LENGTH = 32; DOMAIN_LENGTH = 17; USERNAME_LENGTH = 20; CLIENTNAME_LENGTH = 20; CLIENTADDRESS_LENGTH = 30; type WTS_INFO_CLASS = ( WTSInitialProgram, WTSApplicationName, WTSWorkingDirectory, WTSOEMId, WTSSessionId, WTSUserName, WTSWinStationName, WTSDomainName, WTSConnectState, WTSClientBuildNumber, WTSClientName, WTSClientDirectory, WTSClientProductId, WTSClientHardwareId, WTSClientAddress, WTSClientDisplay, WTSClientProtocolType, WTSIdleTime, WTSLogonTime, WTSIncomingBytes, WTSOutgoingBytes, WTSIncomingFrames, WTSOutgoingFrames, WTSClientInfo, WTSSessionInfo, WTSSessionInfoEx, WTSConfigInfo, WTSValidationInfo, WTSSessionAddressV4, WTSIsRemoteSession ); WTS_CONNECTSTATE_CLASS = ( WTSActive, WTSConnected, WTSConnectQuery, WTSShadow, WTSDisconnected, WTSIdle, WTSListen, WTSReset, WTSDown, WTSInit ); {$IFDEF UNICODE} PWTS_INFO = ^WTS_INFO; WTS_INFO = record State:WTS_CONNECTSTATE_CLASS ; SessionId: DWORD; IncomingBytes :DWORD; OutgoingBytes :DWORD; IncomingFrames:DWORD; OutgoingFrames:DWORD; IncomingCompressedBytes:DWORD; OutgoingCompressedBytes:DWORD; WinStationName: array[0..WINSTATIONNAME_LENGTH - 1] of WCHAR; Domain: array[0..DOMAIN_LENGTH - 1] of WCHAR; UserName:array[0..USERNAME_LENGTH - 1] of WCHAR; ConnectTime:LARGE_INTEGER; DisconnectTime:LARGE_INTEGER; LastInputTime:LARGE_INTEGER; LogonTime:LARGE_INTEGER; CurrentTime:LARGE_INTEGER; end; {$ENDIF} function WTSEnumerateSessions( hServer: THandle; Reserved: DWORD; Version: DWORD; var ppSessionInfo:PWTS_SESSION_INFO; var pCount: DWORD ): BOOL; stdcall; external 'Wtsapi32.dll' name {$IFDEF UNICODE}'WTSEnumerateSessionsW'{$ELSE}'WTSEnumerateSessionsA'{$ENDIF}; function WTSQuerySessionInformation( hServer: NativeUInt; SessionId: DWORD; WTSInfoClass: WTS_INFO_CLASS; var ppBuffer: PLPWSTR; var pBytesReturned: PDWORD): BOOL; stdcall; external 'Wtsapi32.dll' name {$IFDEF UNICODE}'WTSQuerySessionInformationW'{$ELSE}'WTSQuerySessionInformationA'{$ENDIF}; unit test:   //... function GetSessionInfo(id:DWORD):TSessionInfo; var wpSessionInfo:PWTS_INFO; pSessionInfo:PLPWSTR; pBytesReturned:PDWORD; iderr:integer; begin Result.ID:=-1; if id >0 then begin try if (WTSQuerySessionInformation ( WTS_CURRENT_SERVER_HANDLE, id, WTS_INFO_CLASS.WTSSessionInfo, pSessionInfo, pBytesReturned) ) then begin Result.ID := id; wpSessionInfo:=PWTS_INFO(pSessionInfo); //user name Result.user:= wpSessionInfo.UserName; //station name Result.StationName:= wpSessionInfo.WinStationName; //domain name Result.domain:=wpSessionInfo.Domain; //connection status Result.ConnectState:=wpSessionInfo.State; end else begin idErr:=GetLastError; GV_TxtFileLog.Log('[GetSessionInfo] id '+intTostr(id)+' ERR : '+ intToStr(idErr)+' '+SysErrorMessage(idErr),true); end; except on e:exception do GV_TxtFileLog.Log('[GetSessionInfo] id '+intTostr(id)+' EX : '+ e.Message,true); end; end; end; function SF_GetOpenedSessions(var codeErr:integer) :TSessionsInfo; var Sessions, Session: PWTS_SESSION_INFO; NumSessions:DWORD; I:DWORD; SessionInfo:TSessionInfo; pSessionInfo:PLPWSTR; pBytesReturned:PDWORD; wpSessionInfo:PWTS_INFO; id:DWORD; begin SetLength(result,0); codeErr:=0; if WTSEnumerateSessions(WTS_CURRENT_SERVER_HANDLE, 0, 1, Sessions, NumSessions) then begin try if NumSessions > 0 then begin Session := Sessions; for i := 0 to NumSessions do begin id:=Session.SessionId; if id > 0 then begin GV_TxtFileLog.Log('[SF_GetOpenedSessions] GetSessionInfo '+ intToStr(id) ); SessionInfo := GetSessionInfo(id); if SessionInfo.ID>0 then begin SetLength(result, length(Result)+1); Result[length(Result)-1]:= SessionInfo; end; end; Inc(Session); end; end; except codeErr:=GetLastError; GV_TxtFileLog.Log('[SF_GetOpenedSessions] WTSQuerySessionInformation err : '+IntToStr(codeErr)+' '+SysErrorMessage(codeErr), true); end; WTSFreeMemory(Sessions); end else begin codeErr:=GetLastError; GV_TxtFileLog.Log('[SF_GetOpenedSessions] WTSEnumerateSessions err : '+IntToStr(codeErr)+' '+SysErrorMessage(codeErr), true); end; end;     When I call the "SF_GetOpenedSessions" function I get error 87 when this function then calls the "GetSessionInfo" function.
While if I use "GetSessionInfo" passing it the SID of the program it works perfectly... does anyone have an idea why? (I'm going crazy about it!) Compiling in 32 Bit, however, I have no problem.