Socket does not accept correctly in a multithread server - c++

Question

I'm writting an server using the multithread technique.
The idea is :
-I will use a socket (m_Server) to accept when the client connect.
-After accept, I'll use another port (t_Socket[i]) to communicate with that client.
It's simple like that. But it's took me about a week to get this far (Because I have a little bit knowledge about socket and I didn't know anything about multithread before).
Here is my code on server :
#include "stdafx.h"
#include "testServer.h"
#include "afxsock.h"
#include "conio.h"
#include "Player.h"
#include <stdio.h>
#include "../functions.h"
#include <iostream>
using namespace std;
#ifdef _DEBUG
#define new DEBUG_NEW
#endif
#define MAX_THREADS 1
CSocket *p_Socket=new CSocket[MAX_THREADS];
CWinApp theApp;
int count=0;
DWORD WINAPI MyThreadFunction(LPVOID lpParam)
{
int i=count;
cout<<"Send : ";
m_Send(p_Socket[i]);
return 1;
}
int m_Send(CSocket &m_Socket)
{
char Msg[100];
int MsgSize;
cin.getline(Msg,100);
MsgSize=strlen(Msg);
m_Socket.Send(&MsgSize,sizeof(int));
m_Socket.Send(Msg,MsgSize);
return MsgSize;
}
int _tmain(int argc, TCHAR* argv[], TCHAR* envp[])
{
int nRetCode = 0;
HMODULE hModule = ::GetModuleHandle(NULL);
if (hModule != NULL)
{
if (!AfxWinInit(hModule, NULL, ::GetCommandLine(), 0))
{
_tprintf(_T("Fatal Error: MFC initialization failed\n"));
nRetCode = 1;
}
else
{
if(AfxSocketInit()==false)
{
cout<<"Initialize Library Failed"<<endl;
return false;
}
int playerIndex=0;
CSocket m_Server;
HANDLE hThreadArray[MAX_THREADS];
DWORD dwThreadIdArray[MAX_THREADS];
if(m_Server.Create(5770)==0)
{
cout<<"Can not create Socket"<<endl;
cout<<m_Server.GetLastError();
}
else
{
cout<<"Successfully initialize server"<<endl;
}
m_Server.Listen(5);
for(int i=0;i<MAX_THREADS;i++)
{
if(m_Server.Accept(p_Socket[i]))
{
cout<<"Player "<<i+1<<" connected!"<<endl;
}
}
for(int i=0;i<MAX_THREADS;i++)
{
hThreadArray[i]=CreateThread(
NULL,
0,
MyThreadFunction,
NULL,
0,
dwThreadIdArray);
//m_Send(p_Socket[i]); (1)
count++;
}
WaitForMultipleObjects(MAX_THREADS, hThreadArray, TRUE, INFINITE);
for(int i=0;i<MAX_THREADS;i++)
{
p_Socket[i].Close();
}
m_Server.Close();
cout<<"Close all connections"<<endl;
getch();
}
}
else
{
_tprintf(_T("Fatal Error: GetModuleHandle failed\n"));
nRetCode = 1;
}
return nRetCode;
}
The problem is :
-After the m_Server accept a connection. The p_Socket in the multithread function doesn't receive the right connection.
-But, look at the line I write a comment with number (1) : //m_Send(p_Socket[i]); (1).
If I run that line instead of the CreateThread line, the program will doing well. But that will make my program become single threaded.
BTW, the MAX_THREADS I set it to 1 because I want to test the code in the simpliest case. I think the problem in my code is the p_Socket[i] can't pass into a multithread function.
I have search for a solution about this for nearly 2 days. So I decided to post a question here hoping for someone will take a look at it.
Thank you for reading my question and sorry about my bad English.

Answer 1

One big problem is that you use a 'count' global to communicate the array index to the handler thread. That is just wrong and will not work.
Instead of passing the 'dwThreadIdArray' as the last parameter in the CreateThread API, pass in the counter 'i'.
Also, the overall structure of your server is atypical. Usually, the Accept() loop runs forever and ceates a client<>server handler thread immediately after Accept() returns, passing a socket handle/pointer as the last void* param. Your code seems to wait, running a for-loop, until MAX_THREADS clients have connected before creating the handler threads in yet another loop. It this your intended behaviour?