Socket connection between end points on the same machine

Question

When two end points of a socket connection reside on the same machine (Wintel, in this case), do messages between each other traverse onto the NIC card, network medium, and then back to the NIC/machine, and finally to to the other end point?

The reason I am asking is that we've been getting some unexplained socket disconnections reported by the end-points when neither one is calling a socket close (as far as we can tell). Could this be also due to some intermittent network problem?

Answer 1

Typically, two endpoints on the same machine will not go through the network system, unless you explicitally configure your OS to route local packets through an external gateway (on Windows, you can use the command-line ROUTE command for that - a common hack to allow sniffing of local-only packets).