Wi-Fi tethering - how to get list of connected clients

Question

Is there any way to get a the list of connected MAC addresses when my phone is on Wi-Fi tethering mode?

Solution 1

Firstly, you must have a rooted device. When it's done just read dnsmasq.leases file. Usually it is placed at: /data/misc/dhcp/dnsmasq.leases. A structure of the file is pretty simple - each line is a summary of a connected user. The summary has several fields including MAC. I didn't find a possibility to get MAC without root. Please correct me if I'm wrong.

Solution 2

Reading /proc/net/arp would provide the information for both static and DHCP clients that have communicated with the device during the last 60 seconds (configured in /proc/sys/net/ipv4/neigh/wl0.1/gc_stale_time where wl0.1 is the wireless network interface on my phone).

It is available for non-root users too.

Solution 3

@SuppressWarnings("ConstantConditions")
public static String getClientMacByIP(String ip)
{
    String res = "";
    if (ip == null)
        return res;

    String flushCmd = "sh ip -s -s neigh flush all";
    Runtime runtime = Runtime.getRuntime();
    try
    {
        runtime.exec(flushCmd,null,new File("/proc/net"));
    }

    BufferedReader br;
    try
    {
        br = new BufferedReader(new FileReader("/proc/net/arp"));
        String line;
        while ((line = br.readLine()) != null)
        {
            String[] sp = line.split(" +");
            if (sp.length >= 4 && ip.equals(sp[0]))
            {Assistance.Log(sp[0]+sp[2]+sp[3],ALERT_STATES.ALERT_STATE_LOG);
                String mac = sp[3];
                if (mac.matches("..:..:..:..:..:..") && sp[2].equals("0x2"))
                {
                    res = mac;
                    break;
                }
            }
        }

        br.close();
    }
    catch (Exception e)
    {}

    return res;
}

//--------------------------------------------------------

@SuppressWarnings("ConstantConditions")
public static String getClientIPByMac(String mac)
{
    String res = "";
    if (mac == null)
        return res;

    String flushCmd = "sh ip -s -s neigh flush all";
    Runtime runtime = Runtime.getRuntime();
    try
    {
        runtime.exec(flushCmd,null,new File("/proc/net"));
    }

    BufferedReader br;
    try
    {
        br = new BufferedReader(new FileReader("/proc/net/arp"));
        String line;
        while ((line = br.readLine()) != null)
        {
            String[] sp = line.split(" +");
            if (sp.length >= 4 && mac.equals(sp[3]))
            {
                String ip = sp[0];
                if (ip.matches("\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}") && sp[2].equals("0x2"))
                {
                    res = ip;
                    break;
                }
            }
        }

        br.close();
    }
    catch (Exception e)
    {}

    return res;
}

Comments

[user935143]

what about clients connected with static ip not dhcp, they will not appear in the dnsmasq, do you have any idea?

[gumuruh]

Is that true under /proc/net/arp is not always updating the list when the device (client) disconnected from the AP @Roman?

[Kurt Van den Branden]

Please provide some additional info on what your code is doing. It's hard to tell for anyone new what's going on.

[Ritwik Jamuar]

Isn't there any class from android package to do this job?

[truedat101]

While there might be some problems with this answer from the standpoint of the "sh ip -s -s neigh flush all" command, it leads one in the right direction. If connected, /proc/net/arp should have the current neighbords in the file, and this file is accessible from non-rooted devices, making this solution viable to read this file, and parse off the address of the p2p-wlan0-0 device, which on my devices always is in the 192.168.49.* address range.