Re: How to know if a network adapter is connected

Hello,

Binding a socket to an adapter instructs the NDIS to receive only from
this socket. This is the only way I know to identify the network adapter,
where a packet is received. You have to bind the adapter before calling
any send/receive function. Sorry.

Yes i agree but if the adapter is not connected to the network, the bind()
function return SOCKET_ERROR. So i need to bind every socket each time i
call the recv() ????


This is an extract of my source code:

DWORD WINAPI DHCPThread(LPVOID pVoid)
{
SOCKET sockETH, sockUSB;
struct sockaddr_in addrETH;
struct sockaddr_in addrUSB;
struct sockaddr_in addr;
BYTE buf[548];
int lenETH = sizeof(buf);
int lenUSB = sizeof(buf);
int one=1;
int ret;
WSADATA WSAData;

char ChaineIP[25];
int BindUSB, BindETH;



// Initliatize the Winsock dll version 2.0
WSAStartup(MAKEWORD(2,0), &WSAData);


sockETH = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
sockUSB = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if ( (sockETH == INVALID_SOCKET) || (sockUSB == INVALID_SOCKET ) )
{
closesocket(sockETH);
closesocket(sockUSB);
return 0;
} // if

VisuAdresseIPEthernet(); //--> 135.150.11.65 in Chaine[0]
strcpy(&ChaineIP[0], &Chaine[0]);
addrETH.sin_family = AF_INET;
addrETH.sin_addr.s_addr = inet_addr(&ChaineIP[0]);
addrETH.sin_port = htons(67);
BindETH = bind(sockETH, (LPSOCKADDR)&addrETH, sizeof(addrETH)); //bind
ethernet adapter

VisuAdresseIPUSB(); //--> 192.168.0.50 in Chaine[0]
strcpy(&ChaineIP[0], &Chaine[0]);
addrUSB.sin_family = AF_INET;
addrUSB.sin_addr.s_addr = inet_addr(&ChaineIP[0]);
addrUSB.sin_port = htons(67);
BindUSB = bind(sockUSB, (LPSOCKADDR)&addrUSB, sizeof(addrUSB)); //bind
USB adapter


ret=setsockopt(sockETH, SOL_SOCKET, SO_BROADCAST, (const char *) &one,
sizeof(one));
ret=setsockopt(sockUSB, SOL_SOCKET, SO_BROADCAST, (const char *) &one,
sizeof(one));

while (!g_stopDHCP)
{
if ( (lenETH=recv(sockETH, buf, 548, 0))>0)|| (lenUSB=recv(sockUSB, buf,
548, 0))>0) )
{

//...code.....//
//preparation of DHCP buffer.

if (lenUSB > 0)
{
memcpy(&buf[0x3a-0x2a], &AddrIPDHCP_USB, 4);
ret=sendto(sockUSB, buf, lenUSB, 0, (LPSOCKADDR)&addr, sizeof(addr));
}
else if (lenETH > 0)
{
memcpy(&buf[0x3a-0x2a], &AddrIPDHCP_ETH, 4);
ret=sendto(sockETH, buf, lenETH, 0, (LPSOCKADDR)&addr, sizeof(addr));
}

} // if

} // while

shutdown(sockETH, SD_BOTH);
shutdown(sockUSB, SD_BOTH);


closesocket(sockETH);
closesocket(sockUSB);

return 0;

}

I try to bind the socket each time before calling recv().
If you see some errors please.


When you write a service
(http://msdn.microsoft.com/en-us/library/aa446909.aspx) you get an IOCTL
call (http://msdn.microsoft.com/en-us/library/ms891090.aspx), when the
adapter state has changed. You can use this notification to update your
sockets and bind to newly connected adapters.

I don't understand what you want to tell me. I doesn't write a service. This
dhcp server is just a thread in my application. Maybe it's not very clean
but it's the quite easy.

Maybe i could use the GetHostByName function like this:

pHost = gethostbyname("RNDISFN1");
if (pHost!=NULL)
{
//USB connection is valid
}

Thanks


.

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