Java – How do I get the number of devices connected via a phone access point?

As we all know, Android devices have the ability to turn your phone into an access point/hotspot.

Is it possible to programmatically get the number of devices connected to the phone’s WiFi access point?

You can count the connected device on the access point, which gets the hardware MAC address in the following link on Android:
http://www.flattermann.net/2011/02/android-howto-find-the-hardware-mac-address-of-a-remote-host/

Code linked above:

/**
 * Try to extract a hardware MAC address from a given IP address using the
 * ARP cache (/proc/net/arp).<br>
 * <br>
 * We assume that the file has this structure:<br>
 * <br>
 * IP address       HW type     Flags       HW address            Mask     Device
 * 192.168.18.11    0x1         0x2         00:04:20:06:55:1a     *        eth0
 * 192.168.18.36    0x1         0x2         00:22:43:ab:2a:5b     *        eth0
 *
 * @param ip
 * @return the MAC from the ARP cache
 */
public static String getMacFromArpCache(String ip) {
    if (ip == null)
        return null;
    BufferedReader br = null;
    try {
        br = new BufferedReader(new FileReader("/proc/net/arp"));
        String line;
        while ((line = br.readLine()) != null) {
            String[] splitted = line.split(" +");
            if (splitted != null && splitted.length >= 4 && ip.equals(splitted[0])) {
                 Basic sanity check
                String mac = splitted[3];
                if (mac.matches("..:..:..:..:..:..")) {
                    return mac;
                } else {
                    return null;
                }
            }
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        try {
            br.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    return null;
}

Or if you have a problem with the code, try the following code:

 public ArrayList<InetAddress> getConnectedDevices(String YourPhoneIPAddress) {
        ArrayList<InetAddress> ret = new ArrayList<InetAddress>();

LoopCurrentIP = 0;

String IPAddress = "";
        String[] myIPArray = YourPhoneIPAddress.split("\\.");
        InetAddress currentPingAddr;

for (int i = 0; i <= 255; i++) {
            try {

 build the next IP address
                currentPingAddr = InetAddress.getByName(myIPArray[0] + "." +
                        myIPArray[1] + "." +
                        myIPArray[2] + "." +
                        Integer.toString(LoopCurrentIP));
                ad = currentPingAddr.toString();   /////////////////
                Log.d("MyApp",ad);                 //////////////

 50ms Timeout for the "ping"
                if (currentPingAddr.isReachable(50)) {

ret.add(currentPingAddr);
                    ad = currentPingAddr.toString();        /////////////////
                    Log.d("MyApp",ad);                     //////////////
                }
            } catch (UnknownHostException ex) {
            } catch (IOException ex) {
            }

LoopCurrentIP++;
        }
        return ret;
    }