UDP Wrapper Crash

[Vincent DeCampo]

I have been trying to create a Wrapper for UDP functionality. Basically a DLL which can open, configure, send/recieve UDP packets, and close. I create a hidden window to handle UDP events and create a separate thread for the dialog processing.

The problem is, I can open and send, but after that, any other call I make crashes the app.

Here is the code...

 
#COMPILE DLL
#REGISTER NONE
#INCLUDE "WIN32API.INC"
#INCLUDE "WS2_32.INC"
GLOBAL ghInstance AS DWORD
GLOBAL pCALLBACK AS DWORD
GLOBAL hThread AS DWORD
GLOBAL hDlg AS DWORD
TYPE UDP_OBJECT
    pCALLBACK  AS DWORD
    IPAdd      AS ASCIIZ * 20
    PORTNum    AS DWORD
    FILENum    AS DWORD
END TYPE
%UDPMSG_BASE    = %WM_USER+500

PMSG         = 
PMSG_BASE + 800
'--------------------------------------------------------------------------------
'   ** Declarations **
'--------------------------------------------------------------------------------
DECLARE CALLBACK FUNCTION ShowDIALOG1Proc()
DECLARE FUNCTION ShowDIALOG(BYVAL hParent AS DWORD) AS LONG
DECLARE FUNCTION MyThread(BYVAL y AS DWORD) AS DWORD
DECLARE SUB CustomCALLBACK(BYVAL Msg AS LONG)
'-------------------------------------------------------------------------------
' Main DLL entry point called by Windows...
'
FUNCTION LIBMAIN (BYVAL hInstance   AS LONG, _
                  BYVAL fwdReason   AS LONG, _
                  BYVAL lpvReserved AS LONG) AS LONG
    SELECT CASE fwdReason
    CASE %DLL_PROCESS_ATTACH
        'Indicates that the DLL is being loaded by another process (a DLL
        'or EXE is loading the DLL).  DLLs can use this opportunity to
        'initialize any instance or global data, such as arrays.
        ghInstance = hInstance
        ShowDialog (%Hwnd_Desktop)
        THREAD CREATE MyThread(ghInstance) TO hThread
        FUNCTION = 1   'success!
    CASE %DLL_PROCESS_DETACH
        'Indicates that the DLL is being unloaded or detached from the
        'calling application.  DLLs can take this opportunity to clean
        'up all resources for all threads attached and known to the DLL.
        THREAD CLOSE hThread TO hThread
        DIALOG END hDlg
        FUNCTION = 1   'success!
    CASE %DLL_THREAD_ATTACH
        'Indicates that the DLL is being loaded by a new thread in the
        'calling application.  DLLs can use this opportunity to
        'initialize any thread local storage (TLS).
        FUNCTION = 1   'success!
    CASE %DLL_THREAD_DETACH
        'Indicates that the thread is exiting cleanly.  If the DLL has
        'allocated any thread local storage, it should be released.
        FUNCTION = 1   'success!
    END SELECT
END FUNCTION
'--------------------------------------------------------------------------------
'   ** CallBacks **
'--------------------------------------------------------------------------------
CALLBACK FUNCTION ShowDIALOG1Proc()
DIM lParam AS LONG
DIM Count AS LONG
    SELECT CASE CBMSG
        CASE 
PMSG
            IF pCALLBACK > 0 THEN
                lParam = CBLPARAM
                CALL DWORD pCALLBACK USING CustomCALLBACK(lParam)
                FUNCTION = 1
            END IF
'            Select Case lParam
'                Case %FD_READ    'Data is available to be read from the socket.
'                Case %FD_WRITE   'The socket is ready for data to be written.
'                Case %FD_ACCEPT  'The socket is able to accept a new connection.
'                Case %FD_CONNECT 'The connection has been established.
'                Case %FD_CLOSE   'The socket has been closed.
'            End Select
    END SELECT
END FUNCTION
FUNCTION MyThread(BYVAL y AS DWORD) AS DWORD
LOCAL e AS LONG
LOCAL x AS LONG
    DO
        DIALOG DOEVENTS TO e
        DIALOG GET SIZE hDlg TO x, x
    LOOP WHILE x   'When x& = 0, dialog has ended
END FUNCTION
'--------------------------------------------------------------------------------
'   ** Dialogs **
'--------------------------------------------------------------------------------
FUNCTION ShowDIALOG(BYVAL hParent AS DWORD) AS LONG
LOCAL lRslt AS LONG
LOCAL pIP AS LONG
    DIALOG NEW hParent, "UDP", 267, 182, 195, 102, %WS_POPUP _ '%WS_VISIBLE _
        OR %DS_3DLOOK OR %DS_NOFAILCREATE OR %DS_SETFONT, %WS_EX_LEFT OR _
        %WS_EX_LTRREADING OR %WS_EX_RIGHTSCROLLBAR, TO hDlg
    DIALOG SHOW MODELESS hDlg, CALL ShowDIALOG1Proc TO lRslt
    DIALOG SHOW STATE hDlg, %SW_HIDE
    FUNCTION = lRslt
END FUNCTION
'-------------------------------------------------------------------------------
' Examples of exported Subs and functions...
'
FUNCTION UDP_CREATE CDECL () EXPORT AS LONG
    FUNCTION = globalalloc(%GPTR, SIZEOF(UDP_OBJECT))
END FUNCTION
FUNCTION UDP_SETIP CDECL(BYVAL pUDP_OBJECT AS UDP_OBJECT PTR, BYVAL IP AS STRING, BYVAL PortNum AS DWORD) EXPORT AS LONG
    ERRCLEAR
    @pUDP_OBJECT.IPAdd     = IP
    @pUDP_OBJECT.PortNum   = PortNum
    FUNCTION = ERR
END FUNCTION
FUNCTION UDP_CALLBACK CDECL(BYVAL pUDP_OBJECT AS UDP_OBJECT PTR, BYVAL pCALLBK AS DWORD) EXPORT AS LONG
    ERRCLEAR
    pCALLBACK      = pCALLBK
    IF (@pUDP_OBJECT.FileNum > 0) AND (@pUDP_OBJECT.pCALLBACK > 0) THEN
        UDP NOTIFY @pUDP_OBJECT.FileNum, SEND RECV CLOSE TO hDlg AS 
PMSG
    END IF
    FUNCTION = ERR
END FUNCTION
 
FUNCTION UDP_OPEN CDECL(BYVAL pUDP_OBJECT AS UDP_OBJECT PTR) EXPORT AS LONG
    ERRCLEAR
    'Auto Close any previous connection
    IF @pUDP_OBJECT.FileNum > 0 THEN
        UDP CLOSE @pUDP_OBJECT.FileNum
        @pUDP_OBJECT.FileNum   = 0
        @pUDP_OBJECT.pCALLBACK = 0
    END IF
    @pUDP_OBJECT.FileNum = FREEFILE
    UDP OPEN PORT @pUDP_OBJECT.PortNum AS @pUDP_OBJECT.FileNum
    FUNCTION = ERR
END FUNCTION
FUNCTION UDP_CLOSE CDECL(BYVAL pUDP_OBJECT AS UDP_OBJECT PTR) EXPORT AS LONG
    ERRCLEAR
    'Auto close previous connection
    IF @pUDP_OBJECT.FileNum > 0 THEN
        UDP CLOSE @pUDP_OBJECT.FileNum
        @pUDP_OBJECT.FileNum = 0
    END IF
    GlobalFree (pUDP_OBJECT)
    FUNCTION = ERR
END FUNCTION
FUNCTION UDP_SENDDATA CDECL(BYVAL pUDP_OBJECT AS UDP_OBJECT PTR, BYVAL Packet AS STRING ) EXPORT AS LONG
DIM pIP AS LONG
    ERRCLEAR
    'Send Data
    IF @pUDP_OBJECT.FileNum > 0 THEN
        HOST ADDR @pUDP_OBJECT.IPAdd TO pIP
        UDP SEND @pUDP_OBJECT.FileNum, AT pIP, @pUDP_OBJECT.PortNum, Packet
    END IF
    FUNCTION = ERR
    SLEEP 1
END FUNCTION
FUNCTION UDP_GETDATA CDECL(BYVAL pUDP_OBJECT AS UDP_OBJECT PTR, BYREF IPAdd AS LONG, BYREF PortNum AS LONG) EXPORT AS STRING
LOCAL Buffer AS STRING
LOCAL pPort AS LONG
    ERRCLEAR
    'Get Data
    IF @pUDP_OBJECT.FileNum > 0 THEN
        UDP RECV @pUDP_OBJECT.FileNum , FROM IPAdd, PortNum, Buffer
        FUNCTION = Buffer
        EXIT FUNCTION
    END IF
    FUNCTION = "###"
    SLEEP 1
END FUNCTION

I would appreciate it if someone could help me figure out what's wrong.

Thanks
-Vince

[Michael Mattias]

Well, no test EXE provided, but I can see one glaring problem...

CASE %DLL_PROCESS_ATTACH
        'Indicates that the DLL is being loaded by another process (a DLL
        'or EXE is loading the DLL).  DLLs can use this opportunity to
        'initialize any instance or global data, such as arrays.
        ghInstance = hInstance
        ShowDialog (%Hwnd_Desktop)
        THREAD CREATE MyThread(ghInstance) TO hThread

First of all, the dialog is being created on DLL_PROCESS_ATTACH. That's a no-no.

Second, the dialog is being created in the context of the calling thread. For that dialog to execute in a secondary thread the DIALOG NEW must execute from the thread function.

The thread function MyThread is executing a message loop for the queue associated with the second thread... except your window is executing in the context of the calling thread.

That is, if this doesn't crash (whatever "crash" means), it surely won't work anyway.

MCM