[TriLUG] C & sockets programming question

Michael Tharp gxti at partiallystapled.com
Wed Jul 27 19:18:07 EDT 2005


Rick DeNatale wrote:

>I don't claim to be an expert, but I think that there is a basic
>misconception about the relationship between sockets and interfaces
>here. As I understand it a socket represents an end point. An
>interface is a connection to the outside. If there are multiple
>interfaces, it's perfectly possible for packets to flow to and from a
>given socket through different interfaces.  In otherwords, there is a
>little network routing "cloud" between the socket and the interface
>inside the network stack within the OS.  While it's possible to bind
>certain types of sockets to particular interfaces, it's not normally
>done.
>
>If I'm wrong here correct me, I'm here to learn.
>  
>
You're entirely correct, but most hosts have one default route and one 
interface that that route can take, and in this case it's assumed that 
is the goal - to find which. If this were a multihomed router, routes 
change often and packets may not always go out the same interface.
Here it is assumed that there are fixed, single routes out each 
interface and an additional default route which picks one and only one 
outbound interface.

Michael Tharp



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