I think you need to set rules in your routing table in order to route packets based on incoming/outgoing interfaces (ip is your friend here).

As far as I know, a socket at the application layer can give you only information on ip address/port number and not about interface on which it arrived. You might have to dig into writing your own code at the kernel layer, or use one of the utilities like ip to get the information you want.

Just my 2 cents..

In reply to Re^3: Figuring out which network interface a broadcast packet came in on? by linuxfan
in thread Figuring out which network interface a broadcast packet came in on? by lyeoh

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