C / C++ / MFC

14-Feb-08 18:22

Hi guys. I am trying to implement multithreading in a network oriented program. I had a problem when the server would crash when more than one client application connected to it. Thats why i decided to multithread. Now with the threads the client application keeps on saying that the server is not started when i try to connect after catching "WSAECONNREFUSED".

Before i put the threads the program was working just fine only the server crashing problem so i belive it is the server app that has a problem. Below is the code for the worker thread:

//My listening connection
void CServerSocketDlg::OnListen()
{

THREADVALS * pTv = new THREADVALS;// this structure is declared in my .h
AfxBeginThread(AcceptConnection,pTv);

}

UINT AcceptConnection(LPVOID pParam)
{
THREADVALS * pTv = new THREADVALS;
pTv->m_sServerSocket.Listen();
pTv->m_sServerSocket.Accept(pTv->m_sClientSocket);

return 0;
}

//The structure in my .h

typedef struct ACCEPT
{
CMySocket m_sServerSocket,m_sClientSocket;

}THREADVALS;
//Other necessary code in my .h
UINT AcceptConnection(LPVOID pParam);

void Listen();

I have no syntax error it is just refusing to work i dont know why. Please help.

Wamuti: Any man can be an island, but islands to need water around them!
Edmund Burke: No one could make a greater mistake than he who did nothing because he could do only a little.

Rajkumar R14-Feb-08 19:08

Rajkumar R

14-Feb-08 19:08

Wamuti wrote:
THREADVALS * pTv = new THREADVALS;//

in this thread arg, CMySocket m_sServerSocket,m_sClientSocket; are new variable, are they intialised correctly, ie; are they set with the connection parameters.

Wamuti14-Feb-08 19:52

14-Feb-08 19:52

I am checking them right now but let me ask, the way i have done the threads, is it okay?

Wamuti: Any man can be an island, but islands to need water around them!
Edmund Burke: No one could make a greater mistake than he who did nothing because he could do only a little.

Mark Salsbery15-Feb-08 6:49

Mark Salsbery

15-Feb-08 6:49

Your problems have nothing to do with threads.

A single threaded application can handle multiple socket connections.

Yes, there can be advantages to using multiple threads, but your socket
code is already not going to work so adding threads won't help here.

Here's just a few problems with the code you've shown...
1) I don't know what "OnListen()" is
2) There's no benefit in creating a new thread to accept a connection
3) Why does the new thread start a listener socket
4) You can't accept a connection on a listening socket

There's nothing in the code you've shown that indicates that you know how to use
sockets. I would recommend getting that down pat before trying to throw threads at
the problems.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Wamuti17-Feb-08 20:07

17-Feb-08 20:07

Mark Salsbery wrote:
Your problems have nothing to do with threads.

I did not know that. D'Oh! | :doh:

Mark Salsbery wrote:
A single threaded application can handle multiple socket connections.

I'd really appreciate if you could tell me how or recommend a site i can read about that. I woild really appreciate because that's what i need.

Mark Salsbery wrote:
Yes, there can be advantages to using multiple threads, but your socket
code is already not going to work so adding threads won't help here.

You've said that a single threaded application can handle multiple socket connections. What then are the advantages of multiple threads in a socket connection?

Mark Salsbery wrote:
1) I don't know what "OnListen()" is

Okay. It's a function that i have put so that i can initialize in OnInitDialog instead of clogging it with lots of code.

Mark Salsbery wrote:
There's nothing in the code you've shown that indicates that you know how to use
sockets. I would recommend getting that down pat before trying to throw threads at
the problems.

A bit harsh Wink | ;)

but truth be told, you've hit the nail on the head.i am a begginner programmer working with a "Learn Visual C++ in 21 days" and trying my level best. Infact, i am making my very first socket program. Could you please recommend a site.

Wamuti: Any man can be an island, but islands to need water around them!
Edmund Burke: No one could make a greater mistake than he who did nothing because he could do only a little.

Mark Salsbery18-Feb-08 6:19

Mark Salsbery

18-Feb-08 6:19

To use sockets in a single threaded application, you can use the
WSAAsyncSelect() function. This will cause messages to be sent
to a specified window when the socket events you select occur - particularly
useful for when an incoming connection request is received, when there's
data available to be read on a socket, and when a connection is closed.

The advantage of multiple threads is the same advantage as any multithread
application - the app can take advantage of multiple processors for better performance
with parallel processing.

I didn't mean to be harsh at all - just honest. Take the time to learn at least the very
basics of sockets and things will work much better for you in the long run - I know this from
experience Smile | :)

Some basic things to know inside and out -
1) The essential socket APIs (study these in the Winsock SDK):
   socket()
   bind()
   listen()
   accept()
   connect()
   WSAAsyncSelect() (or WSAEventSelect() to use asynchronous socket ops on a separate thread)
   recv()
   send()
   shutdown()
   closesocket()
2) A basic understanding of blocking (synchronous) and non-blocking (asynchronous)
socket modes, and how the mode is changed on a socket.

I wish I had some links but I don't. There's a few great articles here at Code Project
but the search isn't bringing them up at the moment grrr.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Wamuti18-Feb-08 19:23

18-Feb-08 19:23

I wish there was a vote more than 5 Roll eyes | :rolleyes:

thank you so very much. I really do appeciate.

Wamuti: Any man can be an island, but islands to need water around them!
Edmund Burke: No one could make a greater mistake than he who did nothing because he could do only a little.

com

tarak Desai14-Feb-08 17:56

tarak Desai

14-Feb-08 17:56

hi everybody

I wanted to work on COM in vc++
But i donot have any resource of com
So anyone can pls give me some document on com so i can learn it

Thanks in Advance

Re: com

Wamuti14-Feb-08 18:37

14-Feb-08 18:37

i am no expert in com but try :
http://www.cs.umd.edu/~pugh/com/

Wamuti: Any man can be an island, but islands to need water around them!
Edmund Burke: No one could make a greater mistake than he who did nothing because he could do only a little.

Re: com

Wamuti14-Feb-08 18:43

Alignment of Variables Whitin structure

14-Feb-08 18:43

Still i am no expert Wink | ;)

but as you check out the previous also try going to tech tutorials here:

http://www.techtutorials.info/pcom.html

Wamuti: Any man can be an island, but islands to need water around them!
Edmund Burke: No one could make a greater mistake than he who did nothing because he could do only a little.

Re: com

ThatsAlok14-Feb-08 22:25

ThatsAlok

14-Feb-08 22:25

tarak Desai wrote:
I wanted to work on COM in vc++

Buy Developer workshop to ATL/COM 3.0 book, it will provide beginner to expert level information on com!

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow
Never mind - my own stupidity is the source of every "problem" - Mixture

cheers,
Alok Gupta
VC Forum Q&A :- I/IV
Support CRY- Child Relief and You/codeProject$$>

ForNow14-Feb-08 17:53

ForNow

14-Feb-08 17:53

Hi,

I have noticed two strange when I used the Following Typdef

Typdef struct

{
char a;
int b;
}

looking in memory Using The Visual Studio to Build and Debug

the int "b" takes four bytes

and also seems both a and b start boundry divisible by 4

as there are three slack bytes between a's value and b

IS there maybe a compiler option /Noalign to prevent this

Thankx

Maxwell Chen14-Feb-08 18:11

Maxwell Chen

14-Feb-08 18:11

#pragma pack(1)
struct Test {
  int a;
  char b;
};
#pragma pack()

Maxwell Chen

ForNow14-Feb-08 22:05

ForNow

14-Feb-08 22:05

The #pargma pack(1) tell the compiler not to align ????

Iain Clarke, Warrior Programmer

Iain Clarke, Warrior Programmer14-Feb-08 22:28

14-Feb-08 22:28

Have you tried putting #pragma into msdn? then following for pack?

Simple answer is pack(1) tells the compiler to pack on a 1 byte alignment. pop says "go back to what you were doing before".

Iain

Iain Clarke appearing in spite of being begged not to by ^CPallini.

Re: Help with OOP [modified]

ForNow15-Feb-08 0:01

ForNow

15-Feb-08 0:01

thankx

Help with OOP

Lord Kixdemp14-Feb-08 17:22

Lord Kixdemp

14-Feb-08 17:22

Hello everyone!

I'm designing a OOP-based system in C++, and I'm having a little problem. Say I have this:

class Class1
{
    virtual void Draw(Image *a_pImage);
};

class Class2 : public Class1
{
    virtual void Draw(Image *a_pImage);
};

Class1::Draw takes care of ugly low-level stuff, and that's a lot of code. How can Class2::Draw call Class1::Draw so that I don't have to copy-paste all of the code in Class2? In C#, for example, you used base.Draw, but base doesn't exist in C++...
Thanks!

Windows Calculator told me I will die at 28. Frown | :(

Rajkumar R14-Feb-08 17:34

Rajkumar R

14-Feb-08 17:34

void Class2::Draw(Image *a_pImage)
{
// add extra code for Class2 draw

Class1::Draw(a_pImage);

// add extra code for Class2 draw

}

modified on Friday, February 15, 2008 12:15 AM

Lord Kixdemp14-Feb-08 17:38

Lord Kixdemp

14-Feb-08 17:38

Huh? That easy? I was expecting an extremely long message explaining how to delicately trick C++ into doing what I wanted... Thanks , Rajkumar!

Windows Calculator told me I will die at 28. Frown | :(

Rajesh R Subramanian14-Feb-08 20:30

Rajesh R Subramanian

14-Feb-08 20:30

Lord Kixdemp wrote:
Huh? That easy?

"One of the difficulties people have with object-oriented design is that it's too simple to get from the beginning to the end. A mind trained to look for complex solutions is often stumped by this simplicity at first" - Bruce Eckel.

Rajkumar R14-Feb-08 22:12

Rajkumar R

14-Feb-08 22:12

nice quote Smile | :)