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In my college, private IP is used in the range of 10.x.x.x. Every department uses their own routers for their students. The router has IPs in the range of 10.x.x.x.. But, it gives dynamic IPs to the connected devices. My work is find out all the devices connected to the college LAN having an application installed.

So, what I am trying is broadcasting of UDP packets. I will get broadcast address of the current device and send a datagram packet at a particular port. The device will receive the packet from other devices too and from that packet I will know the IP address. But, the issue is in finding a device connected to another router. I don't think it's going to work. How can I find other devices and send data to them?

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  • what about using wireshark to detect every single data inside the network to know every mac address and IP there, its simple, setup wireshark, scan then spy :) but don't forget connect your PC to the main router.
    – Narzan Q.
    Aug 22 '15 at 20:36
  • As I told "My work is find out all the devices connected to the college LAN having an application installed." Sorry for not mentioning that I am working on an android application. And also I don't know how to set up wireshark and all these things..
    – learner
    Aug 22 '15 at 20:50
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    If that's an android app; then you must ask your question at stack overflow, anyway using wireshark will let you know how this whole thing work :) just little hint because what you have said is something hard, scan for devices IP then scan for specific port open in these IPs that app have usually use, in this way you will discover what you want
    – Narzan Q.
    Aug 22 '15 at 21:00
  • can you please tell me one thing? I need to know how data is transferred behind the routers? Does mac address plays a big role here? Since DHCP can give two devices same ip connected with different routers, then I think there should be something more than IP address.
    – learner
    Aug 22 '15 at 21:11
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    you can make something called "sniffing" you can know every device what exactly use in the network even if there is 2 routers, and for that I have said just try wireshark ;) , know how this thing works then build your app
    – Narzan Q.
    Aug 22 '15 at 21:26
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Ok try this program, I have build small program that will let you sniffing your network. wireshark it's hard to use.

  1. Simply have a router and don't connect it to anything.
  2. connect a mobile have that app you want to detect.
  3. Connect PC to that router.
  4. Open my Mini Sniffer

How to use Mini sniffer enter image description here

  1. put the IP of your phone "or the IP of your router to detect everything on the network"
  2. choose the card network you are using. "if your card is wrong the text will be red"

Now Mini sniffer will work automatically just wait a cobble of second try to open anything from your mobile "youtube or anything on the web" sniffer now will show you the port and the data your mobile use. there is a lot of garbage data just ignore it. Try to open the specific app you want to detect and see witch data this app usually use Build your android app or what ever you want, that's it

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  • Would downvote if I could. You may be well-intended narzan, but downloading random executables should be extremely discouraged. Wireshark is open-source, a de facto standard, is well over a decade-old, trusted industry-wide, etc. ... and you would have an asker download an executable with none of those traits for mere convenience ? Hell no.
    – robut
    Aug 28 '15 at 13:16
  • I tried to help him, and I did my best, his choice now :)
    – Narzan Q.
    Aug 30 '15 at 12:17
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By using "Nmap" tool, you can do lot of stuff like pining all the devices and port scanning etc. You should try this tool and google the command or refer the doc to built command depending upon your requirements to scan devices. There is an android app to scan the devices which are connected to a hotstop.

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