How to scan IP and Mac address of all Device Connected to wifi in android accurately?

Question

Hi i am trying to find all devices connected to My WIFI Router from android and ,i need to device Mac address and local ip address of each device (Including iOT Devices) , right now , i am trying to find from ARP cache table . but sometime in the scan some devices are missing , it is not so accurate .

My Code :

 List<LocalDeviceInfo> devicesInfos = new ArrayList<>();


        BufferedReader bufferedReader = null;

        try {
            bufferedReader = new BufferedReader(new FileReader("/proc/net/arp"));

            String line;
            while ((line = bufferedReader.readLine()) != null) {
                String[] splitted = line.split(" +");
                if (splitted != null && splitted.length >= 4) {
                    String ip = splitted[0];
                    String mac = splitted[3];
                    if (mac.matches("..:..:..:..:..:..")) {
                        LocalDeviceInfo thisNode = new LocalDeviceInfo(ip, mac);
                        devicesInfos.add(thisNode);
                    }
                }
            }

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally{
            try {
                bufferedReader.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        // Print Description
        for (LocalDeviceInfo devicesInfo :devicesInfos)
        {
            System.out.print("✅");
            System.out.println("IP : "+devicesInfo.getIp());
            System.out.println("Mac : "+devicesInfo.getMacAddress());
        }

---

How can i scan all devices (IP address and Mac address) in android accurately .

---

Keeshakeeshond

Answer 1

I found the solution of my problem , most of devices was not in the system arp table , so you need to Ping each of device at first time , once you ping that device its will be stored in System ARP Table Which is stored at (/proc/net/arp)

Pinging All devices with ip: ( First you need to find your device's IP Address , than you can determine the subnet mask and you can start pining from (0-255)

Code:

public  void startPingService(Context context)
{
  List<LocalDeviceInfo> deviceInfoList  = new ArrayList<LocalDeviceInfo>();
    try {

        WifiManager mWifiManager = (WifiManager) context.getSystemService(Context.WIFI_SERVICE);
        WifiInfo mWifiInfo = mWifiManager.getConnectionInfo();
        String subnet = getSubnetAddress(mWifiManager.getDhcpInfo().gateway);


        for (int i=1;i<255;i++){

            String host = subnet + "." + i;

            if (InetAddress.getByName(host).isReachable(timeout)){

                String strMacAddress = getMacAddressFromIP(host);

                Log.w("DeviceDiscovery", "Reachable Host: " + String.valueOf(host) +" and Mac : "+strMacAddress+" is reachable!");

                    LocalDeviceInfo localDeviceInfo = new LocalDeviceInfo(host,strMacAddress);
                    deviceInfoList.add(localDeviceInfo);
             }
            else
            {
                Log.e("DeviceDiscovery", "❌ Not Reachable Host: " + String.valueOf(host));

            }
        }


    }
    catch(Exception e){
        //System.out.println(e);
    }


}


private String getSubnetAddress(int address)
{
    String ipString = String.format(
            "%d.%d.%d",
            (address & 0xff),
            (address >> 8 & 0xff),
            (address >> 16 & 0xff));

    return ipString;
}

Get Mac address from ARP cache Table

public String getMacAddressFromIP(@NonNull String ipFinding)
{

    Log.i("IPScanning","Scan was started!");
    List<LocalDeviceInfo> antarDevicesInfos = new ArrayList<>();


    BufferedReader bufferedReader = null;

    try {
        bufferedReader = new BufferedReader(new FileReader("/proc/net/arp"));

        String line;
        while ((line = bufferedReader.readLine()) != null) {
            String[] splitted = line.split(" +");
            if (splitted != null && splitted.length >= 4) {
                String ip = splitted[0];
                String mac = splitted[3];
                if (mac.matches("..:..:..:..:..:..")) {

                    if (ip.equalsIgnoreCase(ipFinding))
                    {
                        return mac;
                    }
                }
            }
        }

    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } finally{
        try {
            bufferedReader.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    return "00:00:00:00";
}

You need these permission too:

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

Keeshakeeshond

Right..Adding the permissions is very necessary which is sometimes left while focusing on the code – Crispa

Using the ping helped a lot. InetAddress.getByName(host.getHostAddress()).isReachable(3000). Is there another way to get the mac address? What if the network computer does not reply back to ping/icmp? – Haymes

Answer 2

Actually, you only need to ping the broadcast address of the device's network to make the ICMP ECHO request go to every and each machine on the network. No need to ping separately. On the other hand, some devices don't respond to pings like these as a "security precaution". It's up to you.

Then, do what the code in the other answer does - parse /proc/net/arp which contains the ARP cache. From that special file in procfs you will find out the MAC addresses of network devices in your network. (Posting this as an answer because I do not have enough reputation yet to add this as a comment to the other answer)

Shifra