C / C++ / MFC

17-Oct-09 7:17

I am writing a multithreaded TCP server(MFC).
The steps I am following are:-
1.)Create a listen socket.
2.)listen on specific port.
3.)spin individual thread for every client that connects.

My application is a dialog based MFC App.But it crashes when a client connects to it. Frown | :(

While spinning the THREAD what parameter should I pass to the thread's main function(CDialog Object or listening socket). Confused | :confused:

what type of thread should I Create WORKER or UI.
My code is like this:-

// sockDlg.cpp : implementation file

BOOL CsockDlg::OnInitDialog()
{
	.
        .
        .
	// TODO: Add extra initialization here
	int m_iPort = 4000;

	m_sConnectSocket.SetParent(this);      // Object of CMySocket derived from CAsyncSocket
	m_sListenSocket.SetParent(this);       // // Object of CMySocket derived from CAsyncSocket

	m_sListenSocket.Create(m_iPort);
	m_sListenSocket.Listen();

	return TRUE;  // return TRUE  unless you set the focus to a control
}

void CsockDlg::OnAccept(void)
{
	//m_sListenSocket.Accept(m_sConnectSocket);
	AfxBeginThread(ThreadServer, this);
}

UINT CsockDlg::ThreadServer(LPVOID pParam)
{
	CsockDlg* C = (CsockDlg*)pParam;
	CAsyncSocket client;
	C->m_sListenSocket.Accept(client);
	//::Sleep(60000);
	return 0;
}

I have seen many examples for console servers but how to implement it on a Dialog Based Application?????

Future Lies in Present.
Manmohan Bishnoi

Moak17-Oct-09 8:21

Moak

17-Oct-09 8:21

Manmohan29 wrote:
My application is a dialog based MFC App.But it crashes when a client connects to it.Frown
While spinning the THREAD what parameter should I pass to the thread's main function(CDialog Object or listening socket).Confused

Hi again!

1) CAsyncSocket is event based and there is no need to use multithreading. This kind of networking model provides everything in a single thread context.
2) Did you try an example from the links I gave you a day ago? I would be much easier for us to help when you start from a working example.
3) What do you mean with "spinning a thread"?

Happy coding
/M

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Manmohan2917-Oct-09 9:12

17-Oct-09 9:12

Thanks for the advice.
I was becoming a little bit lazy to search the examples(Today is Diwali[Indian Festival]). But now i will look them.

I meant "creating a thread for every client" for "spinning a thread".

Future Lies in Present.
Manmohan Bishnoi

Manmohan2917-Oct-09 9:22

17-Oct-09 9:22

This is the code for threaded server's accepting function

void AcceptConnections(SOCKET ListeningSocket)
{
    sockaddr_in sinRemote;
    int nAddrSize = sizeof(sinRemote);

    while (1) {
        SOCKET sd = accept(ListeningSocket, (sockaddr*)&sinRemote,
                &nAddrSize);
        if (sd != INVALID_SOCKET) {
            cout << "Accepted connection from " <<
                    inet_ntoa(sinRemote.sin_addr) << ":" <<
                    ntohs(sinRemote.sin_port) << "." <<
                    endl;

            DWORD nThreadID;
            CreateThread(0, 0, EchoHandler, (void*)sd, 0, &nThreadID);
        }
        else {
            cerr << WSAGetLastErrorMessage("accept() failed") << 
                    endl;
            return;
        }
    }
}

we accepting the connection

SOCKET sd = accept(ListeningSocket, (sockaddr*)&amp;sinRemote,
                &amp;nAddrSize);

and, then creating a thread to handle client

CreateThread(0, 0, EchoHandler, (void*)sd, 0, &amp;nThreadID);

Here we are passing the connecting socket to the thread function.
And I am puzzled how to pass the connecting socket to thread's function in my application.

" Future Lies in Present. "
Manmohan Bishnoi

Rajesh R Subramanian17-Oct-09 10:28

Rajesh R Subramanian

17-Oct-09 10:28

1. Your first post shows that you're using MFC. You could so use CAsyncSocket like the other poster suggested to you.

2. Creating a thread for each connection is inefficient, and can you imagine what would happen when the number of connections keep raising? If you would like to use threads to serve the client requests, just accept the connections in the UI thread and use a thread pool for the serving purpose.

3. Using CreateThread in an MFC program is an extremely bad idea. If you are using MFC, you *must* use AfxBeginThread to create a worker thread. (Generally there is no reason to call CreateThread at all. If you are not using MFC, you should still be calling _beginthreadex)

4. It looks like you are deriving a dialog class from a socket class? Can't a socket class be contained within your dialog class instead?

“Follow your bliss.” – Joseph Campbell

Moak17-Oct-09 11:12

Moak

17-Oct-09 11:12

Just a comment, Rajesh: The poster showed in his previous post that CsockDlg is a CDialog derived class. He tries to convert a multithreaded-socket-API example into an even-based-CAsyncSocket version, if I am not mistaken. Because those two networking models are very different, it's probably easier to start with a fresh working MFC example. Smile | :)

Cheers
/M

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Manmohan2918-Oct-09 0:48

18-Oct-09 0:48

Here's an excellent tutorial for what I was looking.
Please have a look.
http://www.flounder.com/kb192570.htm[^]

Future Lies in Present.
Manmohan Bishnoi

Rajesh R Subramanian18-Oct-09 2:38

Rajesh R Subramanian

18-Oct-09 2:38

I'm glad you found something that'd be of use to you. Dr. Joseph is a terrific guy and his site is loaded with useful articles. On an additional note, he is supporting my view of using a thread pool: Even if the message that comes in from the socket requires considerable computing, the more effective method is to have all the sockets running in the main GUI thread, and have the extensive computing handled by threads from a thread pool.

Important: Never delete any of your messages that you post to this board. It is a RULE! Read the guidelines. I find a question has been posted to me and come here to reply, but I see that it has been removed.

“Follow your bliss.” – Joseph Campbell

Manmohan2918-Oct-09 4:03

18-Oct-09 4:03

I didn't deleted my post intentionally. Just hit the Post Message Button in a hurry instead of preview.
Don't misunderstand me.

Future Lies in Present.
Manmohan Bishnoi

Is there any existing function to change language ID to language String?

Moak18-Oct-09 8:04

Moak

18-Oct-09 8:04

This isn't a simple example and the use of threads together with CAsyncSocket is unjustified and inefficient. Joseph M. Newcomer is a deeply respect member in developer circles, however I would say that the link you found was never intended as a MFC networking tutorial. Mixing asynchronous sockets and threads make little sense, here is an overview of basic server concepts:

a) blocking servers (handling only one request at a time, then wait again blocking)
b) threaded servers (handling simultaneous requests, one thread for every new socket, maybe from a pool).
c) asynchronous server (handling simultaneous requests, one thread context will handle all sockets)
d) variants such as IO completition ports

Instead of trying to convert one example code you had into a different thing, it would be easier if you learn about different networking concepts and start with simple examples. There are so many choices and CAsyncSocket might not be the best alternative in the long term (there are known problems). Perhaps have a look at some of the links I gave you. Smile | :)

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includeh1017-Oct-09 3:11

Re: Is there any existing function to change language ID to language String?

17-Oct-09 3:11

Language ID is a WORD from function GetSystemDefaultLangID().

I think there are existing user/system functions which can convert language ID to String, such as:

0x03 (SUBLANG_ARABIC_EGYPT) to string "Arabic (Egypt)"

so that I can save my time to redo them one by one.

Any hints/links?

Thanks

Michael Schubert17-Oct-09 5:22

Michael Schubert

17-Oct-09 5:22

The mappings are in "winnt.h". If you want to map IDs to strings like "Arabic (Egypt)" you'll have to do it yourself.

C++ advanced literature pls?

lawsmlt17-Oct-09 3:02

lawsmlt

17-Oct-09 3:02

Hi all,
I'm currently doing my final year dissertation, being on wireless transmission in a client-server model. Can anyone suggest any dense literature about technical detailed c++ programming such as enabling communication between server and additional programs (such as ffmpeg), excessing USB devices (such as webcam, mic, video capture card) and the like..

Thanks in advance, any help will be much appreciated Smile | :)

how to undef a typedef?

includeh1016-Oct-09 23:35

16-Oct-09 23:35

typedef struct _ABC
{
//....
}ABC;

how to undef ABC here?

this is for correcting/updating VC lib errors.

Cedric Moonen16-Oct-09 23:50

Cedric Moonen

16-Oct-09 23:50

includeh10 wrote:
this is for correcting/updating VC lib errors.

Could you elaborate a bit on that ? Because I think you are trying to solve the problem in a wrong way.

Cédric Moonen
Software developer

Charting control [v2.0]
OpenGL game tutorial in C++

includeh1017-Oct-09 0:21

17-Oct-09 0:21

Cedric Moonen wrote:
Could you elaborate a bit on that ? Because I think you are trying to solve the problem in a wrong way.

how do you get a feeling of "wrong way"?

for this <winbase.h>

typedef struct _OSVERSIONINFOEXA {
    DWORD dwOSVersionInfoSize;
    DWORD dwMajorVersion;
    DWORD dwMinorVersion;
    DWORD dwBuildNumber;
    DWORD dwPlatformId;
    CHAR   szCSDVersion[ 128 ];     // Maintenance string for PSS usage
    WORD wServicePackMajor;
    WORD wServicePackMinor;
    WORD wReserved[2];
} OSVERSIONINFOEXA, *POSVERSIONINFOEXA, *LPOSVERSIONINFOEXA;
typedef struct _OSVERSIONINFOEXW {
    DWORD dwOSVersionInfoSize;
    DWORD dwMajorVersion;
    DWORD dwMinorVersion;
    DWORD dwBuildNumber;
    DWORD dwPlatformId;
    WCHAR  szCSDVersion[ 128 ];     // Maintenance string for PSS usage
    WORD wServicePackMajor;
    WORD wServicePackMinor;
    WORD wReserved[2];
} OSVERSIONINFOEXW, *POSVERSIONINFOEXW, *LPOSVERSIONINFOEXW;

Maximilien17-Oct-09 1:18

Maximilien

17-Oct-09 1:18

You cannot remove a typedef.

These are 2 versions of the same struct, one for unicode (W) and one for non-unicode(A)

There should be a third typedef that will use one or the other depending of your project settings.

something like

#ifdef unicode
#define  OSVERSIONINFOEXW OSVERSIONINFOEX
#else
#define  OSVERSIONINFOEXA OSVERSIONINFOEX
#endif

Normally one will use the third typedef so that the code can be easily converted to/from unicode without having to manually change the code.

So, what't the errors/problems you originally had ? compilation errors ? runtime errors?

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includeh1017-Oct-09 2:04