Winsock Trouble..

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Overflowz

Joined: 03 Sep 2010
Posts: 1046

Overflowz 17 Dec 2011, 12:22

Hello everyone, I got some problems on winsock when trying to receive same time from different sockets..
First of all, I have 2 sockets, and first is waiting for data to be received, the second will be created in thread, which will wait to receive another data.. But problem is that, program won't continue executing, until thread's recv will receive data.. I was thinking a lot but I don't understand what is the problem.. Here's code:

Code:

proc blah
......
@@:
        invoke recv,[hSock],dstbuff,1024,0
        invoke send,[rSock],dstbuff,eax,0
        push eax
        invoke CreateThread,0,0,threadproc,0,0,0
        cinvoke printf,<"[+] Packets sent!",0x0a,0>
        pop eax
        test eax,eax
        jg @b
.cleanup:
        invoke closesocket,[hSock]
        invoke closesocket,[rSock]
        invoke WSACleanup
        invoke Sleep,100
        ret
endp

proc threadproc stdcall
        invoke recv,[rSock],srcbuff,1024,0 ;<-- stucks here until it receives data! WHY ?
        invoke send,[hSock],srcbuff,eax,0
       ret
endp

17 Dec 2011, 12:22

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20451
Location: In your JS exploiting you and your system

revolution 17 Dec 2011, 12:51

RTFM

TFM wrote:

If no incoming data is available at the socket, the recv call waits for data to arrive unless the socket is nonblocking. In this case, a value of SOCKET_ERROR is returned with the error code set to WSAEWOULDBLOCK. The select, WSAAsyncSelect, or WSAEventSelect calls can be used to determine when more data arrives.

17 Dec 2011, 12:51

Overflowz

Joined: 03 Sep 2010
Posts: 1046

Overflowz 17 Dec 2011, 12:54

revolution
I know that but:
1) It's running to another thread. Why thread are pausing my program ?
2) How to use blocking sockets ? I have no idea.

17 Dec 2011, 12:54

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20451
Location: In your JS exploiting you and your system

revolution 17 Dec 2011, 13:02

Overflowz wrote:

I know that but:

If you took the time to explain what you know and what you tried then we won't just assume you didn't know and you would get better quality answers. Wink

Overflowz wrote:

1) It's running to another thread. Why thread are pausing my program ?

Your main thread also has a recv. And since you didn't post all your code I have no idea what you are doing or what you mean by "pausing your program".

Overflowz wrote:

2) How to use blocking sockets ? I have no idea.

TFM explains it.

17 Dec 2011, 13:02

Overflowz

Joined: 03 Sep 2010
Posts: 1046

Overflowz 17 Dec 2011, 13:26

I posted the code, which are running in different thread and I have problem only there, not else anywhere, so, I said thread's recv is waiting data until it receives and by that time, program execution is passed to only that thread, I mean, program waits that thread and then continues execution (I hate English).
and what TFM mean I really don't know. Be more understandable please.

17 Dec 2011, 13:26

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20451
Location: In your JS exploiting you and your system

revolution 17 Dec 2011, 13:44

So after the thread is created does you code print "[+] Packets sent!"? And after printing "[+] Packets sent!" your code loops around and waits on another recv

Code:

@@:
        invoke recv,[hSock],dstbuff,1024,0 ;wait here also
        invoke send,[rSock],dstbuff,eax,0

How do you know where your code is waiting? With multiple threads it can be tricky to know which is waiting for what. How do you use your debugger to determine what happened?

I suspect you are looking in the wrong place, and that is why you need to post all the code, or at the very least a working example showing the problem. Give us something we can compile and run to see what is happening. Help us to help you.

The reason I suspect you are looking in the wrong place is because a single thread waiting on a blocking API call cannot "pause you whole program". The other threads will continue to run normally. You have to find out where the other threads are and what they are waiting on.

17 Dec 2011, 13:44

Overflowz

Joined: 03 Sep 2010
Posts: 1046

Overflowz 17 Dec 2011, 14:03

revolution
I found problem, sorry, problem is in loop. I'm creating thread in loop even if threadproc is not receiving data..
Thank you Smile

17 Dec 2011, 14:03

Overflowz

Joined: 03 Sep 2010
Posts: 1046

Overflowz 17 Dec 2011, 17:46

Not going to open another thread, just asking here.. How should I set option to socket to be Non-Blocking ? Should I use ReadFile/WriteFile instead of recv/send ?

17 Dec 2011, 17:46

Overflowz

Joined: 03 Sep 2010
Posts: 1046

Overflowz 18 Dec 2011, 08:45

Never mind, I found. It is done with ioctlsocket API.

18 Dec 2011, 08:45

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