How to Multicast (send) to first NIC?

Question

I found recently that if I have a dial-up connection (this is for a kiosk) and a local area network connection, when the dial-up connection is established (with internet acc

Answer 1

Use GetAdaptersAddresses() to enumerate all available interface IP addresses.

IP_MULTICAST_IF is for IPv4 addresses only. It expects you to pass a DWORD value containing the desired IPv4 address (in network byte order) to setsockopt(), eg:

DWORD dwIP = ...;
setsockopt(sock, IPPROTO_IP, IP_MULTICAST_IF, (char *)&dwIP, sizeof(dwIP));