Hi all, I have 2 questions: 1. How to get the source ip by winsock? 2. Is there a simpler way to broadcast message to all connected clients instead of storing all clients'' ip in an array?

Use UDP. here a sample class that does the job
class CZSocket
{
public:
CZSocket(){
memset(&_local_sin,0,sizeof(_local_sin));
memset(&_remote_sin,0,sizeof(_remote_sin));
memset(&_mcastGrp,0,sizeof(_mcastGrp));
_sock = INVALID_SOCKET;
};
virtual ~CZSocket(){};

void Listen(int i)
{
listen(_sock,i);
}
operator SOCKET(){return _sock;}
operator HANDLE(){return (HANDLE)_sock;}

bool AsClient(DWORD ip, int port)
{
_sock = socket(AF_INET,SOCK_STREAM,0);
if(_sock == INVALID_SOCKET)
{
_error = WSAGetLastError();
return false;
}

_local_sin.sin_family = AF_INET;
_local_sin.sin_addr.s_addr = htonl(ip);
_local_sin.sin_port = htons(port);

_error = connect(_sock,(const struct sockaddr*)&_local_sin,sizeof(_local_sin));
return _error==0;
}

int Send(BYTE* pb, int len)
{
return send(_sock,(char *)pb,len,0);
}


int Receive(BYTE* pb, int len)
{
return recv(_sock,(char *)pb,len,0);
}


bool AsClient(const char* sip, int port)
{
_sock = socket(AF_INET,SOCK_STREAM,0);
if(_sock == INVALID_SOCKET)
{
_error = WSAGetLastError();
return false;
}

_local_sin.sin_family = AF_INET;
_local_sin.sin_addr.s_addr = inet_addr(sip);
_local_sin.sin_port = htons(port);
_error = connect(_sock,(const struct sockaddr*)&_local_sin,sizeof(_local_sin));
return _error==0;
}



bool Accept(CZSocket& cliSock)
{
int clilen = sizeof(cliSock._remote_sin);
cliSock._sock = accept(_sock,
(struct sockaddr*)&cliSock._remote_sin,
&clilen);
if(_sock == INVALID_SOCKET)
{
_error = WSAGetLastError();
return false;
}
return true;
}


void Close()
{
if(_sock>0)
{
if(_groupmember )
{
_error = setsockopt (_sock, IPPROTO_IP, IP_DROP_MEMBERSHIP, (char FAR *)&_mcastGrp, sizeof (_mcastGrp)) ;
}
shutdown (_sock, 0x02);
closesocket(_sock);
}
_sock=INVALID_SOCKET;
}

int AsListener(int port)
{
_sock = socket(AF_INET,SOCK_STREAM,0);
if(_sock < 0)
{
return _error = WSAGetLastError();
}
_local_sin.sin_family = AF_INET;
_local_sin.sin_addr.s_addr = htonl(INADDR_ANY);
_local_sin.sin_port = htons(port);
_error = bind(_sock,(struct sockaddr*)&_local_sin,sizeof(_local_sin));
if(_error < 0)
{
_error = WSAGetLastError();
Close();
return _error;
}
return 0;
}


int AsMulticastReceiver(const char* ipGrp, int port)
{
_sock = socket (AF_INET, SOCK_DGRAM, 0);
if (_sock == INVALID_SOCKET)
{
return _error = WSAGetLastError();
}
//server receives
_local_sin.sin_family = AF_INET;
_local_sin.sin_port = htons (port);
_local_sin.sin_addr.s_addr = htonl (INADDR_ANY);

_error = bind (_sock, (struct sockaddr FAR *) &_local_sin, sizeof (_local_sin));
if (_error == INVALID_SOCKET)
{
_error = WSAGetLastError();
Close();
return _error;
}

//join the multicast group
_mcastGrp.imr_multiaddr.s_addr = inet_addr (ipGrp);
_mcastGrp.imr_interface.s_addr = INADDR_ANY;

_error = setsockopt (_sock, IPPROTO_IP, IP_ADD_MEMBERSHIP, (char FAR *)&_mcastGrp, sizeof (_mcastGrp)) ;
if (_error == INVALID_SOCKET)
{
_error = WSAGetLastError();
Close();
return _error;
}
_groupmember = true;

return 0;
}

int MulticastRec(BYTE* pbuff, int length)
{
int iRecvLen = sizeof (_remote_sin);

_error = recvfrom (_sock, (char*)pbuff, length, 0,(struct sockaddr FAR *) &_remote_sin, &iRecvLen);
if (_error == INVALID_SOCKET)
{
Close();
return _error;
}
return _error;
}


int AsMulticastSender()
{
_sock = socket(AF_INET,SOCK_DGRAM,0);
if(_sock == INVALID_SOCKET)
{
return _error = WSAGetLastError();
}

// from server
_local_sin.sin_family = AF_INET;
_local_sin.sin_port = htons (0);
_local_sin.sin_addr.s_addr = htonl (INADDR_ANY);

if (bind (_sock, (struct sockaddr*) &_local_sin, sizeof (_local_sin)) == SOCKET_ERROR)
{
_error = WSAGetLastError();
Close();
return _error;
}
int iOptVal = 64; //time to live
if (setsockopt (_sock, IPPROTO_IP, IP_MULTICAST_TTL,
(char FAR *)&iOptVal, sizeof (int)) == SOCKET_ERROR)
{
_error = WSAGetLastError();
Close();
return _error;
}

return 0;
}

int SendTo(const char* ipGrp, int port, BYTE* buff, int length)
{
// to client
_remote_sin.sin_family = AF_INET;
_remote_sin.sin_port = htons (port);
_remote_sin.sin_addr.s_addr = inet_addr(ipGrp);
_error = sendto (_sock, (char*)buff, length, 0, (struct sockaddr FAR *) &_remote_sin, sizeof (_remote_sin)) ;
if(SOCKET_ERROR == _error)
{
Close();
return _error;
}
return _error;
}

struct ip_mreq _mcastGrp;
struct sockaddr_in _local_sin; // source
struct sockaddr_in _remote_sin; // dest
SOCKET _sock;
int _error;
bool _groupmember;
};

// server
CZSocket smultic;
smultic.AsMulticastSender();
// broadacst to all subscribers "234.100.99.97"
smultic.SendTo("234.100.99.97", 1234, (BYTE*)&netBuff,
sizeof(netBuff));
smultic.Close()

and the client

CZSocket pDgram;
pDgram.AsMulticastReceiver("234.100.99.97", 1234)) // this connects to multicast IP 234.100.99.97
int oneshoot = pDgram.MulticastRec(buffer, bufferSize);
pDgram.Close();

Works fine

MCO

damn yo.. stick that in a couple of [source][/source] tags