How do I make Winsock use a specific network interface?
Before I answer the stated question, keep in mind that the routing layer of the stack exists to handle this for you. If your setup isn’t working the way you want, maybe you just need to change the routing tables. (This is done with the route and netstat command-line programs.) There are two common reasons you might want to force the stack to use a particular network interface. The first is when you only want your server program to handle incoming connections on a particular interface. For example, perhaps one of the interfaces on your machine is an Ethernet card connected to a private LAN and the other is a USB DSL modem connected to the big bad Internet. In such a case, listening only on the trusted network is safer, if you can get away with it. The other reason is that you have two or more possible outgoing routes, and you want your client program to connect using a particular one without the routing layer getting in the way. You can do both of these things with the bind() function.
