When running something like this on a large scale to capture all traffic going across a network, you'd typically use a "network packet broker" (cf. Google) that

When running something like this on a large scale to capture all traffic going across a network, you'd typically use a "network packet broker" (cf. Google) that sends a copy of all traffic to the machine(s) running this software. Your hypothetical application server would not even be aware that this was taking place.