Finding the device in LAN network which is sending packets that do not allow phone to go to sleep

Bear with me because I think this is a really odd situation. It all started by noticing that my android phone (and some other phones) loses more than 10% of battery during night while doing nothing (only wifi and mobile-data was active). Using dumpsys batterystats, it showed me this strange wakeups: As it is evident from the log, the phone gets woken up roughly every 3 seconds. I first thought of some app in my phone but even deleting all apps did not solve the problem (not even factory reset). I went further and flashed various custom roms (with different kernels) without any apps (not even Google Play services) but the log still showed the unknown wakeups. I suspect that maybe there is something from the outside of the phone which was causing this behavior (because it show up only when connecting to my home wifi LAN; with other wifi networks or using mobile-data everything was normal). And it turned out that my Android Box was causing this odd behavior (connected to the same wifi network) because as soon as I disconnected the Android Box from my Lan network, there was no more unknown wakeups (sending some packets to the phones which are in the same network and causing them not to go to sleep) My questions are: 1. What are these packets that the Android Box is sending? 2. Given the type of these packets, is there any tool that can scan the network and identify which device is sending them?