Active computer on a WLAN

[Farabi]

I created this function to check how many computers active on a WLAN, the function is works but it make my software cannot be terminated, anyone know why?

Code Select Expand


fInet struct
sock dword 0
lpszurl dword 0
fInet ends

.code
fConnectToUrl proc uses esi edi lps:dword,hWnd:dword,lpszHostName:dword,nPort:dword
LOCAL a:sockaddr_in
LOCAL wsadata:WSADATA

invoke WSAStartup,202h,addr wsadata
.if eax!=0
xor eax,eax
dec eax
ret
.endif

assume esi:ptr fInet
mov esi,lps
invoke socket,AF_INET,SOCK_STREAM,0     ; Create a stream socket for internet use
.if eax!=INVALID_SOCKET

    mov [esi].sock,eax
invoke WSAAsyncSelect,[esi].sock,hWnd,WM_FSOCKET,FD_CONNECT+FD_READ+FD_CLOSE+FD_WRITE+FD_ACCEPT
.else
invoke MessageBox,hWnd,CADD("Internet connection initialization error"),CADD("Unknown cause"),MB_OK
.endif

push lpszHostName
pop [esi].lpszurl

mov a.sin_family, AF_INET
invoke htons, nPort
mov a.sin_port,ax
invoke gethostbyname, lpszHostName
.if eax==0
invoke PERR
ret
.endif
mov eax,[eax+12]

mov eax,[eax]                      ; copy the pointer to the actual IP address into eax
mov eax,[eax]                      ; copy IP address into eax
mov a.sin_addr,eax

invoke connect,[esi].sock,addr a,sizeof a
.if eax==SOCKET_ERROR
invoke WSAGetLastError 
;invoke PERR
.endif



assume esi:nothing

ret
fConnectToUrl endp

GetLocalAddress proc uses esi edi ebx lptzAddr:dword
LOCAL fakeBuffer:DWORD
LOCAL lnBuffer:DWORD
LOCAL tempBuffer[128]:BYTE
LOCAL tempItem:LV_ITEM
LOCAL sci:dword
LOCAL wsadata:WSADATA

; Get TCP table in fake buffer of 1 byte. This will cause a
; buffer overflow error, the lnBuffer var will be filled with
; the required amount of memory.
invoke WSAStartup,202h,addr wsadata
.if eax!=0
xor eax,eax
dec eax
ret
.endif
invoke gethostbyname,0
.if eax==0
invoke PERR
ret
.endif
mov eax,[eax+12]
mov eax,[eax]
mov ecx,[eax]
invoke inet_ntoa,ecx
push eax
invoke memfill, lptzAddr,16,0
pop eax
invoke lstrcat,lptzAddr,eax

ret
GetLocalAddress endp


ScanComputer proc uses esi edi hWnd:dword,uMsg:dword,wParam:dword,lParam:dword
LOCAL buff[256]:dword
LOCAL buff2[8]:dword
LOCAL adcnt,off_data:dword
local a:fInet

invoke GetLocalAddress,addr local_addr
invoke mAlloc,(16*256)+4
mov add_table,eax

xor ecx,ecx
loop_check:
push ecx
mov adcnt,ecx
invoke memfill,addr buff,1024,0
invoke lstrcat,addr buff,CADD("192.168.1.")
invoke dw2a,adcnt,addr buff2
invoke lstrcat,addr buff,addr buff2
invoke fConnectToUrl,addr a,hWnd,addr buff,139
invoke Sleep,100
invoke send,a.sock,CADD("Test"),4,0
.if eax!=SOCKET_ERROR
xor edx,edx
mov ecx,add_table
mov eax,[ecx]
mov ecx,16
mul ecx
add eax,4

add eax,add_table
mov ecx,eax
invoke MemCopy,addr buff,ecx,16
mov ecx,add_table
inc dword ptr[ecx]
.endif
invoke closesocket,a.sock
pop ecx
inc ecx
cmp ecx,25
jl loop_check


mov ecx,add_table
add ecx,4
invoke MessageBox,0,ecx,0,0

ret
ScanComputer endp



how to use

Code Select Expand


invoke ScanComputer,hWnd,0,0,0


[ecube]

toss in a invoke GetErrDescription,0 (is from masm32lib) throughout your code to see if it's being reached, as that's the only way I can see exitprocess not working.

[Farabi]

Messagebox on the end of the computerscan function is called so I guess nothing wrong on the scancomputer function, the mistake is somewhere.

[ecube]

are you using invoke ExitProcess,0 to exit? maybe toss the getdescrip call after that.

[oex]

Hey Onan,

It has very long pauses (about 15 seconds) in the main loop.... I thought this was the crash.... is it not?

[ecube]

I havent tested the code but I can tell you memcopy moves the length into ecx, so it maybe overriding your string, try another register

[Farabi]

Hey Onan,

It has very long pauses (about 15 seconds) in the main loop.... I thought this was the crash.... is it not?

It was not that long in here, it took about 2 second.

[Farabi]

are you using invoke ExitProcess,0 to exit? maybe toss the getdescrip call after that.

Yeah I used that on the WM_DESTROY, I cant found the getdescrip function.

[oex]

OK I reduced the checks to 2 from 25 and the application quit ok.... I'm not confident yet that I'm sending the right params I have set:

    .data

local_addr  dd  0
add_table   dd  0

in my test atm

.... It sounds like maybe you have a stray register somewhere and it is infinate looping.... What is the CPU % when it doesnt quit?

[ecube]

Code Select Expand


invoke MemCopy,addr buff,ecx,16  <---check this, when you call MemCopy it moves 16 into ecx, so it overrrides it


[oex]

Code Select Expand


invoke MemCopy,addr buff,ecx,16  <---check this, when you call MemCopy it moves 16 into ecx, so it overrrides it


I dont believe this matters because ecx isnt used after the function call:
mov ecx, add_table
rather than
mov add_table, ecx

[ecube]

it does matter because what hes passing in ecx isn't being used at all in the function, it's being overridden.

[oex]

it does matter because what hes passing in ecx isn't being used at all in the function, it's being overridden.

Where exactly?

MemCopy proc public uses esi edi Source:PTR BYTE,Dest:PTR BYTE,ln:DWORD
    cld
    mov esi, [Source]
    mov edi, [Dest]
    mov ecx, [ln]

I do however see a possible issue here:

         mov ecx, add_table
         mov eax, [ecx]

[ecube]

it does matter because what hes passing in ecx isn't being used at all in the function, it's being overridden.

Where exactly?

MemCopy proc public uses esi edi Source:PTR BYTE,Dest:PTR BYTE,ln:DWORD
    cld
    mov esi, [Source]
    mov edi, [Dest]
    mov ecx, [ln]         <--- 16 is moved here

invoke MemCopy,addr buff,ecx,16 <----hes passing the destination in ecx

[oex]

it does matter because what hes passing in ecx isn't being used at all in the function, it's being overridden.

Where exactly?

MemCopy proc public uses esi edi Source:PTR BYTE,Dest:PTR BYTE,ln:DWORD
    cld
    mov esi, [Source]
    mov edi, [Dest]
    mov ecx, [ln]         <--- 16 is moved here

invoke MemCopy,addr buff,ecx,16 <----hes passing the destination in ecx

I'm sorry I'm still not seeing it.... ecx is moved to edi before it is destroyed by ln.... it is not used again after that except to be written to.... Do you mean the ecx before MemCopy?