.ELSEIF eax==WM_TIMER
                invoke ShowDownloadSpeed
        .ELSEIF eax==WM_CREATE
                invoke CreateStatusWindow,WS_CHILD+WS_VISIBLE+SBARS_SIZEGRIP,NULL,hWnd,IDC_STATUS     ; Create the status bar
                mov hwndStatus,eax      ; Create the status bar
                invoke SendMessage,hwndStatus,SB_SETPARTS,2,addr PartWidth
        .ELSEIF eax==WM_SOCKET
                mov eax,lParam
                .if ax==FD_CONNECT      ; if the socket is connected
                        push eax
                        pop eax
                        shr eax,16      ; If there is an error during connect process, the error code is returned in the high word of lParam                        
                        .if ax==NULL    ; If there is no error, proceed to send the request
                                invoke SendRequest
                        .else
                                invoke ReconnectIfPossible
                        .endif                                
                .elseif ax==FD_READ
                        shr eax,16      ; Check if there is an error code in the high word of lParam
                        .if eax==0
                                invoke ReadSocket
                        .else
                                invoke ShowSocketError
                        .endif
                .elseif ax==FD_CLOSE    ; When the connection is closed from the other end, it marks the end of the file
                        shr eax,16
                        .if eax==0      ; Check if there is some error
                                invoke CloseTheSock
                        .else
                                .if eax==WSAECONNRESET || eax==WSAECONNABORTED
                                        invoke CloseTheSock
                                .else
                                        invoke ShowSocketError
                                .endif
                        .endif
               .endif                                
        .ELSEIF eax==WM_COMMAND
                mov eax,wParam
                .if lParam==0
                        .if ax==IDM_CONNECT     ; When the user presses connect button or connect menu item.
                                mov Resuming,FALSE      ; Assume that the server cannot resume download
                                mov FileHandle,0        ; We use the value of FileHandle to check whether the file was closed
                                mov TimerID,0           ; We use the value of TimerID in the same manner as FileHandle
                                mov eax,OFFSET URLProc
                                invoke DialogBoxParam,hInstance,addr URLDialogName,hWnd,eax,0
                                .if eax==TRUE           ; If the user types in a url
                                        invoke ConnectSocket
                                .endif
                        .elseif ax==IDM_EXIT
                                invoke DestroyWindow,hWnd
                        .else
                                invoke MessageBox,hWnd, addr AboutMessage, addr AppName,MB_OK or MB_ICONINFORMATION
                        .endif
                .else
                        .if ax==IDC_CONNECT
                                invoke SendMessage,hWnd,WM_COMMAND,IDM_CONNECT,0
                        .elseif ax==IDC_EXIT
                                invoke DestroyWindow,hWnd
                        .endif
                .endif
        .ELSE
                invoke DefWindowProc,hWnd,uMsg,wParam,lParam
                ret
        .ENDIF
        xor eax,eax
        ret
WndProc endp
;======================================================================
;                       ShowSocketError
;======================================================================
; This procedure is called to display the error message on the screen in
; case of FD_CONNECT, FD_READ and FD_CLOSE notification.
;======================================================================
ShowSocketError PROC
        invoke TranslateErrorCode,eax,addr ErrorString
        invoke MessageBox,NULL,addr ErrorString,addr AppName,MB_OK+MB_ICONERROR
        invoke CloseSock
        invoke EnableControls
        ret
ShowSocketError ENDP

;========================================================================
;                           URLProc
;========================================================================
;  This is the dialog procedure of the dialog that receives url from the 
;  user
;========================================================================
URLProc PROC hDlg:DWORD,uMsg:DWORD,wParam:DWORD,lParam:DWORD
        .if uMsg==WM_CLOSE
                invoke EndDialog,hDlg,0
        .elseif uMsg==WM_INITDIALOG
                mov wParam,IDC_EDIT1       ; Set the focus to the edit control
        .elseif uMsg==WM_COMMAND
                mov eax,wParam
                .if ax==IDC_OK
                        shr eax,16
                        .if ax==BN_CLICKED      ; If the user clicks ok button
                                invoke GetDlgItemText,hDlg,IDC_EDIT1,addr URLString,512
                                .if eax!=0   ; If the user doesn't type in some string, don't close the dialog box
                                        invoke EndDialog,hDlg,1
                                .else
                                        invoke GetDlgItem,hDlg,IDC_EDIT1
                                        invoke SetFocus,eax
                                .endif
                        .endif
                .elseif ax==IDC_CANCEL
                        shr eax,16
                        .if ax==BN_CLICKED
                                invoke SendMessage,hDlg,WM_CLOSE,0,0
                        .endif
                .endif
        .else
                mov eax,FALSE
                ret
        .endif
        mov eax,TRUE
        ret
URLProc ENDP
;======================================================================
;                               String2Dword
;======================================================================
; This procedure takes an address of a string and converts it to a dword
; value which it returns in eax
;======================================================================
String2Dword proc uses ecx edi edx esi String:DWORD
        xor ecx,ecx
        mov edi,String
        invoke lstrlen,String
        .while eax!=0
                xor edx,edx
                mov dl,byte ptr [edi]
                sub dl,"0"      ; subtrack each digit with "0" to convert it to hex value
                mov esi,eax
                dec esi
                push eax
                mov eax,edx
                push ebx
                mov ebx,10
                .while esi > 0
                        mul ebx
                        dec esi
                .endw
                pop ebx
                add ecx,eax
                pop eax
                inc edi
                dec eax
        .endw
        mov eax,ecx
        ret
String2Dword endp

;======================================================================
;                               ParseHeader
;======================================================================
; This procedure takes the address of HTTP header and finds the file size
;======================================================================
ParseHeader PROC uses esi ecx edi Header:DWORD
        LOCAL MyHeader[512]:BYTE
        invoke lstrcpy,addr MyHeader,Header
        invoke CharLower,addr MyHeader ; Convert the http header to lower case
        .if Resuming==FALSE     ; in the case that we resume download, we don't have to
                                ; search the header for content length again
                invoke lstrlen,addr MyHeader
                mov ecx,eax
                lea edi,MyHeader          ; begin searching for "content-length:"
Rescan:
                mov al,"c"              ;   by scanning for its first char, "c"
                repne scasb
                jne  NoLength           ; If not found, something is wrong
                push ecx                ; If "c" is found, it's still not certain
                                ;   that it's the start of the
                                ;   "content-length:" string. So we must
                                ;   save all registers so that we can
                                ;   resume scanning.
                push edi
                dec  edi                ; move back to the "c" character
                mov ecx,15              ; 15 --> the length of "content-length:"
                mov esi,offset Content
                repe cmpsb              ; compare if the string that starts with "c"
                                ; is identical to "content-length"
                mov  esi,edi            ; save edi which points to the first byte
                                ; of the length (if it's "content-length")
                pop  edi
                pop  ecx
                jne  Rescan             ; if the strings didn't match, rescan the http header
                mov edi,offset ContentString
                .while (byte ptr [esi]!=0Dh)
                        .if byte ptr [esi]!=20h
                                mov al,byte ptr [esi]
                                mov byte ptr [edi],al
                                inc edi
                        .endif
                        inc esi
                .endw
                mov byte ptr [edi],0
                invoke String2Dword,addr ContentString
                mov ContentLength,eax
        .endif
Find_status_code:
        invoke lstrlen,addr MyHeader
        mov ecx,eax
        lea edi,MyHeader
        mov al," "
        repne scasb
        .if byte ptr [edi]==" "
                repe scasb
                dec edi
        .endif
        mov ecx,3
        mov esi,edi
        mov edi,offset StatusCode
        rep movsb
        mov eax,TRUE
        ret
NoLength:
        mov  ContentLength,0
        jmp  Find_status_code
Unsuccessful:
        mov eax,FALSE
        ret
ParseHeader endp

;=========================================================================
;                               ParseURL
;=========================================================================
; This function parses the url string for host name, relative URL and http
; port
;-------------------------------------------------------------------------
ParseURL PROC uses esi edi URL:DWORD
        LOCAL MyURL[512]:BYTE
        LOCAL URLLength:DWORD

        invoke lstrlen,URL
        mov URLLength,eax
        mov ecx,eax             ; Trim the spaces at the start of the url string, if any
        mov edi,URL
        mov al,20h
        repe scasb
        dec edi
        invoke lstrcpy,addr MyURL,edi           ; We don't want to modify the original url string since we have to modify the cases of the url
        invoke lstrcpy,URL,addr MyURL
        invoke lstrlen,URL
        mov URLLength,eax
        invoke RtlFillMemory,addr HostName,501,0   ; fill HostName and RelativeURL with zeroes
        invoke CharLower,addr MyURL             ; change to lower case for ease of comparison
        lea edi,MyURL
        mov esi,offset HTTP             ; check if the url starts with "http://"
        mov ecx,7
        repe cmpsb
        jne No_HTTP
        mov eax,URLLength       ; if it is, substract the length of url string by 7 to
        sub eax,7               ; account for the length of "http://" string
        mov URLLength,eax
        jmp Common_parse
No_HTTP:
        lea edi,MyURL
Common_parse:
        push edi
        invoke lstrcpy,addr MyURL,URL
        pop edi
        xor ecx,ecx
        mov esi,offset HostName
        mov HTTPPort,80         ; Default port =80
        .while ecx < URLLength
                .if byte ptr [edi]=="/"         ; if "/" is found, it denotes the end of the host name string
                        invoke lstrcpy,addr RelativeURL,edi     ; and the start of the relative url string
                        .break
                .elseif byte ptr [edi]==":"     ; if ":" is found, it means an HTTP port is specified in the url
                        inc ecx
                        inc edi
                        invoke RtlFillMemory,addr PortString,10,0
                        mov eax,offset PortString
                        .while (byte ptr [edi]!="/") && (byte ptr [edi]!=0)
                                mov dl,byte ptr [edi]
                                mov byte ptr [eax],dl
                                inc eax
                                inc ecx
                                inc edi
                        .endw