ASM Community

Can someone tell me why this prog aint receiving all the data properly. It works only if I use MessageBox inside the recv loop.



.386
.model flat, stdcall
option casemap:none

include \masm32\include\windows.inc
include \masm32\include\wsock32.inc
includelib \masm32\lib\wsock32.lib
include \masm32\include\kernel32.inc
includelib \masm32\lib\kernel32.lib
include \masm32\include\user32.inc
includelib \masm32\lib\user32.lib
include C:\ASM\string.inc

.data

SOCKSET STRUCT
dwCount dword ?
dwSocket dword ?
SOCKSET ENDS

wsadata WSADATA <?>
fdset SOCKSET <?>
timeout timeval <?>
p sockaddr_in <?>
sock dword ?

sockopt dword 1
recbuf byte 1001 dup (0)
stobuf byte 64000 dup (0)
port dword 80, 0
ipaddress byte "216.17.149.78", 0
slcterror1 byte "select error: write", 0
slcterror2 byte "select error: read", 0
nosend byte "couldn't send data", 0
blockerror byte "couldn't set socket mode", 0
noinit byte "couldn't initialise winsock", 0
nosock byte "couldn't create a socket", 0
noconnect byte "couldn't connect to server", 0
closed byte "connection closed", 0
finished byte "FINISHED", 0
filename byte "bleh.txt", 0
bufwrite dword ?

get byte 'GET /index.html', 10, 13
byte 'Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, */*', 10, 13
byte 'Accept-Language: en-gb', 10, 13
byte 'Accept-Encoding: gzip, deflate', 10, 13
byte 'User-Agent: Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)', 10, 13
byte 'Host: www.rec.com', 10, 13
byte 'Connection: Keep-Alive', 10, 13, 10, 13, 0 ;258 chars

;=========
.code

start:

@@initialise_winsock:
invoke WSAStartup, 101h, addr wsadata
cmp eax, NULL
jne @@noinit

@@setup_socket:
invoke socket, AF_INET, SOCK_STREAM, 0
cmp eax, INVALID_SOCKET
je @@nosock
mov , eax
invoke htons, 80
mov p.sin_port, ax
invoke inet_addr, addr ipaddress
mov p.sin_addr, eax
mov p.sin_family, AF_INET

@@connect_to_server:
invoke connect, , addr p, sizeof p
cmp eax, SOCKET_ERROR
je @@noconnect

@@make_non_blocking:
invoke ioctlsocket, , FIONBIO, addr sockopt
cmp eax, SOCKET_ERROR
je @@blockerror

@@check_for_sock_write:
mov eax,
mov fdset.dwSocket, eax
mov fdset.dwCount, 1
mov timeout.tv_sec, 3
mov timeout.tv_usec, NULL
invoke select, NULL, NULL, addr fdset, NULL, addr timeout
cmp eax, NULL
je @@slcterror1
cmp eax, SOCKET_ERROR
je @@slcterror1

@@send_request_data:
invoke lstrlen, addr get
invoke send, , addr get, eax, NULL
cmp eax, SOCKET_ERROR
je @@no_send

@@check_for_sock_read:
mov eax,
mov fdset.dwSocket, eax
mov fdset.dwCount, 1
mov timeout.tv_sec, 20
mov timeout.tv_usec, NULL
invoke select, NULL, addr fdset, NULL, NULL, addr timeout
cmp eax, NULL
je @@slcterror2
cmp eax, SOCKET_ERROR
je @@slcterror2

@@receive_data_loop:
invoke recv, , addr recbuf, 1000, NULL
cmp eax, SOCKET_ERROR
je @@finish1
cmp eax, NULL
je @@closed
mov , 0
;invoke MessageBox, NULL, addr recbuf, NULL, MB_OK
invoke _strcat, addr stobuf, addr recbuf ; my append-a-string proc
jmp @@receive_data_loop

@@closed:
invoke MessageBox, NULL, addr closed, addr finished, MB_OK
jmp @@finish2

@@finish1:
invoke _strcat, addr stobuf, addr recbuf ; append the collected data to recbuf

@@finish2:
invoke closesocket,
invoke WSACleanup
invoke CreateFile,\
addr filename,\
GENERIC_WRITE,\
FILE_SHARE_READ or\
FILE_SHARE_WRITE,\
NULL,\
CREATE_ALWAYS,\
FILE_ATTRIBUTE_NORMAL,\
NULL

push eax
invoke lstrlen, addr stobuf
mov edx, eax
pop eax

invoke WriteFile,\
eax,\
addr stobuf,\
edx,\
addr bufwrite,\
NULL

invoke MessageBox, NULL, addr stobuf, addr finished, MB_OK
jmp @@exitproc





;==============
@@no_send:
invoke MessageBox, NULL, addr nosend, NULL, MB_OK
jmp @@exitproc

@@blockerror:
invoke MessageBox, NULL, addr blockerror, NULL, MB_OK
jmp @@exitproc

@@slcterror1:
invoke MessageBox, NULL, addr slcterror1, NULL, MB_OK
jmp @@exitproc

@@slcterror2:
invoke MessageBox, NULL, addr slcterror2, NULL, MB_OK
jmp @@exitproc

@@nosock:
invoke MessageBox, NULL, addr nosock, NULL, MB_OK
jmp @@exitproc

@@noinit:
invoke MessageBox, NULL, addr noinit, NULL, MB_OK
jmp @@exitproc

@@noconnect:
invoke MessageBox, NULL, addr noconnect, NULL, MB_OK

@@exitproc:
invoke ExitProcess, 1

end start

PuffCool: I don't think that's the solution as removing that code makes select useless..
However I tried to assemble your code but of course I didn't had the string.inc, so I just changed all your strcat functions to the lstrcat windows API. Then it ran fine and showed the finish messagebox with full content and no crashes.. So I think there's a bug in your string.inc

Thomas

Thomas

When you ran the application after assembling, did you take a look at the text file that was created? When I used the source as provided, the text file was incomplete, whereas when I took out the selected code, the file was complete. I'm not saying what I did is a proper solution, but just thought i'd bring it to attention.

I am also curious to the solution, however I tried to have the application download an exe file with no success. If anyone knows the proper way, I would gladly appreciate any help.

Puffcool: I just had a quick look and overlooked that (sorry for that), thanks

I solved the problem, I guess. Right now, you wait for the socket to have data available (@@check_for_sock_read), but this doesn't mean ALL data is available. It just means, at least one byte is available.. Your code assumes it can just keep on reading until it returns 0 but this isn't true.. It can occur that no data is available at some point. In that case, recv will fail with WSAEWOULDBLOCK, because you are in non-blocking mode, recv fails instead of blocking (i.e. waiting for more data).
Your error is that on any error, you just quit. Instead, first check if you have a WSAEWOULDBLOCK error, and if it is, call select again to wait for more data.. Here is the working code:

.....

@@receive_data_loop: 

invoke recv, [sock], addr recbuf, 1000, NULL 

cmp eax, SOCKET_ERROR 

je @@error  ;<<<<<<<<< MODIFIED!!!

.....



; ADDED!!!:

@@error:

invoke	WSAGetLastError

.IF eax==WSAEWOULDBLOCK

   jmp @@check_for_sock_read

.ENDIF

int 3 ;breakpoint, some other error occured

....

The int 3 is just a breakpoint.. If you reach that point some other error has occurred..

By making these changes I got the full html file in the output file so I think this will do.

Thomas

I think this can only have to do with the way of displaying.. As WriteFile and MessageBox use exactly the same data it has to be this.
Maybe there's a LF of the CRLF missing somewhere, or something else a messagebox displays different than your text editor..
I wouldn't worry about it,

Thomas