Problem when Creating AsyncSocket

[lsvedin]

I have two network cards on my machine and I retrieve their info by the following code, mainly their IP addresses:

hostent *host = NULL;
char hostName[128] = "";
sockaddr_in sockAddr;
char m_UIWIp[2][16];
CString tempIP;

gethostname(hostName, sizeof(hostName));

host = gethostbyname(hostName);

if (!host)
{
	AfxMessageBox("Error getting local IP address", MB_OK);
}
else
{
	//set IPs for both network cards
	for (int i = 0; host->h_addr_list[i]; i++)
	{
		memcpy(&sockAddr.sin_addr, host->h_addr_list[i], host->h_length);
		tempIP =  inet_ntoa(sockAddr.sin_addr);

		<snip>

		m_UIWIp[0] = tempIP
	}
}

Later I user this address in setting up some sockets:

for (i = 0; i < 2; i++)
{
	if (!m_WrTCMSockFd[i].Create(WRITE_PORT,SOCK_DGRAM , FD_WRITE, m_UIWIp[i]))
	{
		nLastError = m_WrTCMSockFd[i].GetLastError();	// Obtain the error code
		switch (nLastError)
		{
			case WSAEAFNOSUPPORT:
				MidOutMsg,"Address family is not supported\n";
				break;
			case WSAEMFILE:
				MidOutMsg="No more file descriptors available\n";
				break;
			case WSAENOBUFS:
				MidOutMsg="No buffer space is available\n";
				break;
			case WSAEPROTONOSUPPORT:
				MidOutMsg="Specified port not supported\n";
				break;
			case WSAEPROTOTYPE:
				MidOutMsg="Specified port is the wrong type for this socket\n";
				break;
			case WSAESOCKTNOSUPPORT:
				MidOutMsg="Specified socket type is not supported in this address family\n";
				break;
			default:
				MidOutMsg="Unrecognized error\n";
				break;
		}
	}
}

The problem was one of the network cards wasn't connected to anything and so the IP address being returned was "". So when I tried creating the socket, I was getting the error of WSAEADDRNOTAVAIL which isn't on the list of valid returns for the Create function.

The problem that I was having was the bad address was the first ip address and when I tried creating the second ip address, nothing could be created.

Now if the valid address was first, I was able to create it, but not if it was second.

I know I can solve the problem of making sure that the address is valid, but why was the second Create failing if the first Create had a "" for an address

[Andreas Masur]

[ Moved thread ]