Local network mapper with ARP requests

What is the best/lighter way to scan/nmap for other devices in the 16 bit block on the same lan where the connected board running blynk is?

Could you please describe your goal? Iā€™m not sure I understood you correctly.

Basically, in few words the goal is to be able to know what devices are connected to the LAN where the blynk device is connected. This can be done sending ARP packets I guess, using UPnP, SSDP or whatever network discovery protocol is best suited.

You have to create some sort of broadcast protocol to detect Blynk devices and have the devices respond to it with a code of some sort. UDP will probably be handy for this. I think there are a couple libraries out there who can do that.