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Get Android WiFi "net.hostname" from code

Posted by: admin June 15, 2020 Leave a comment

Questions:

When an Android device connects to a wifi AP, it identifies itself with a name like:

android_cc1dec12345e6054

How can that string be obtained from within an Android app? Not for the purpose of changing it, just for readout.

EDIT:
This is a screenshot of my router’s web interface, showing a list of all connected devices. Note the two Android devices on the list — How can that string be read from Java code running on the device?

Router's connection list

How to&Answers:

Building off of @Merlevede’s answer, here’s a quick and dirty way to get the property. It’s a private API, so it’s subject to change, but this code hasn’t been modified since at least Android 1.5 so it’s probably safe to use.

import android.os.Build;
import java.lang.reflect.Method;

/**
 * Retrieves the net.hostname system property
 * @param defValue the value to be returned if the hostname could
 * not be resolved
 */
public static String getHostName(String defValue) {
    try {
        Method getString = Build.class.getDeclaredMethod("getString", String.class);
        getString.setAccessible(true);
        return getString.invoke(null, "net.hostname").toString();
    } catch (Exception ex) {
        return defValue;
    }
}

Answer:

Use the NetworkInterface object to enumerate the interfaces and get the canonical host name from the interfaces’ InetAddress. Since you want the wifi name, as a shortcut you can query for wlan0 directly and if that fails you can enumerate them all like this:

import android.test.InstrumentationTestCase;
import android.util.Log;

import java.net.InetAddress;
import java.net.NetworkInterface;
import java.util.Enumeration;

public class NetworkInterfaceTest extends InstrumentationTestCase {
    private static final String TAG = NetworkInterfaceTest.class.getSimpleName();
    public void testNetworkName() throws Exception {
        Enumeration<NetworkInterface> it_ni = NetworkInterface.getNetworkInterfaces();
        while (it_ni.hasMoreElements()) {
            NetworkInterface ni = it_ni.nextElement();
            Enumeration<InetAddress> it_ia = ni.getInetAddresses();
            if (it_ia.hasMoreElements()) {
                Log.i(TAG, "++ NI:   " + ni.getDisplayName());
                while (it_ia.hasMoreElements()) {
                    InetAddress ia = it_ia.nextElement();
                    Log.i(TAG, "-- IA:   " + ia.getCanonicalHostName());
                    Log.i(TAG, "-- host: " + ia.getHostAddress());
                }
            }
        }
    }
}

That will give you an output like this:

TestRunner﹕ started: testNetworkName
++ NI:   lo
-- IA:   ::1%1
-- host: ::1%1
-- IA:   localhost
-- host: 127.0.0.1
++ NI:   p2p0
-- IA:   fe80::1234:1234:1234:1234%p2p0
-- host: fe80::1234:1234:1234:1234%p2p0
++ NI:   wlan0
-- IA:   fe80::1234:1234:1234:1234%wlan0
-- host: fe80::1234:1234:1234:1234%wlan0
-- IA:   android-1234567812345678   <--- right here
-- host: 192.168.1.234

Tip: if InetAddress.getCanonicalHostName().equals(InetAddress.getHostAddress()) you can ignore it as it’s not a “real” name.

Answer:

I don’t know if this helps but here I go.

From a unix shell (you can download any Terminal app in Google Play), you can get the hostname by typing

getprop net.hostname

Of course this is not what you want… but… on the other hand, here is information on how to execute a unix command from java. Maybe by combining these two you get what you’re looking for.

Answer:

For java:

you can get the property by below:

String str = SystemProperties.get("net.hostname");

Answer:

I used jiangze ren’s answer and modified it.

Now you can get hostname by getting IP address of device:

   WifiManager wm = (WifiManager) getApplicationContext().getSystemService(WIFI_SERVICE);
                        final String ip = Formatter.formatIpAddress(wm.getConnectionInfo().getIpAddress());
                        InetAddress address = InetAddress.getByName(ip);
                        System.out.println(address.getHostName());  // <-- host name is here and not localhost!

Answer:

Try this:

Class<?> c = Class.forName("android.os.SystemProperties");
            Method get = c.getMethod("get", String.class, String.class);
            String serialNumber = (String) get.invoke(c, "net.hostname", "Error");
            if (serialNumber.equals("Error")) {
                serialNumber = (String) get.invoke(c, "net.hostname", "Error");
            }

Answer:

you can use the code below:

InetAddress address = InetAddress.getLocalHost();  
System.out.println(address.getHostName());  // <-- host name is here!

And actually, you can more info using this function.
such as…
other devices hostname which are in the same network.