[android] How to get IP address of the device from code?

Is it possible to get the IP address of the device using some code?

public static String getLocalIpAddress() {
    try {
        for (Enumeration<NetworkInterface> en = NetworkInterface.getNetworkInterfaces(); en.hasMoreElements();) {
            NetworkInterface intf = en.nextElement();
            for (Enumeration<InetAddress> enumIpAddr = intf.getInetAddresses(); enumIpAddr.hasMoreElements();) {
                InetAddress inetAddress = enumIpAddr.nextElement();
                if (!inetAddress.isLoopbackAddress() && inetAddress instanceof Inet4Address) {
                    return inetAddress.getHostAddress();
                }
            }
        }
    } catch (SocketException ex) {
        ex.printStackTrace();
    }
    return null;
}

I've added inetAddress instanceof Inet4Address to check if it is a ipv4 address.

Compiling some of the ideas to get the wifi ip from the WifiManager in a nicer kotlin solution:

private fun getWifiIp(context: Context): String? {
  return context.getSystemService<WifiManager>().let {
     when {
      it == null -> "No wifi available"
      !it.isWifiEnabled -> "Wifi is disabled"
      it.connectionInfo == null -> "Wifi not connected"
      else -> {
        val ip = it.connectionInfo.ipAddress
        ((ip and 0xFF).toString() + "." + (ip shr 8 and 0xFF) + "." + (ip shr 16 and 0xFF) + "." + (ip shr 24 and 0xFF))
      }
    }
  }
}

Alternatively you can get the ip adresses of ip4 loopback devices via the NetworkInterface:

fun getNetworkIp4LoopbackIps(): Map<String, String> = try {
  NetworkInterface.getNetworkInterfaces()
    .asSequence()
    .associate { it.displayName to it.ip4LoopbackIps() }
    .filterValues { it.isNotEmpty() }
} catch (ex: Exception) {
  emptyMap()
}

private fun NetworkInterface.ip4LoopbackIps() =
  inetAddresses.asSequence()
    .filter { !it.isLoopbackAddress && it is Inet4Address }
    .map { it.hostAddress }
    .filter { it.isNotEmpty() }
    .joinToString()

Recently, an IP address is still returned by getLocalIpAddress() despite being disconnected from the network (no service indicator). It means the IP address displayed in the Settings> About phone> Status was different from what the application thought.

I have implemented a workaround by adding this code before:

ConnectivityManager cm = getConnectivityManager();
NetworkInfo net = cm.getActiveNetworkInfo();
if ((null == net) || !net.isConnectedOrConnecting()) {
    return null;
}

Does that ring a bell to anyone?

I used following code: The reason I used hashCode was because I was getting some garbage values appended to the ip address when I used getHostAddress . But hashCode worked really well for me as then I can use Formatter to get the ip address with correct formatting.

Here is the example output :

1.using getHostAddress : ***** IP=fe80::65ca:a13d:ea5a:233d%rmnet_sdio0

2.using hashCode and Formatter : ***** IP=238.194.77.212

As you can see 2nd methods gives me exactly what I need.

public String getLocalIpAddress() {
    try {
        for (Enumeration<NetworkInterface> en = NetworkInterface.getNetworkInterfaces(); en.hasMoreElements();) {
            NetworkInterface intf = en.nextElement();
            for (Enumeration<InetAddress> enumIpAddr = intf.getInetAddresses(); enumIpAddr.hasMoreElements();) {
                InetAddress inetAddress = enumIpAddr.nextElement();
                if (!inetAddress.isLoopbackAddress()) {
                    String ip = Formatter.formatIpAddress(inetAddress.hashCode());
                    Log.i(TAG, "***** IP="+ ip);
                    return ip;
                }
            }
        }
    } catch (SocketException ex) {
        Log.e(TAG, ex.toString());
    }
    return null;
}

Though there's a correct answer, I share my answer here and hope that this way will more convenience.

WifiManager wifiMan = (WifiManager) context.getSystemService(Context.WIFI_SERVICE);
WifiInfo wifiInf = wifiMan.getConnectionInfo();
int ipAddress = wifiInf.getIpAddress();
String ip = String.format("%d.%d.%d.%d", (ipAddress & 0xff),(ipAddress >> 8 & 0xff),(ipAddress >> 16 & 0xff),(ipAddress >> 24 & 0xff));

You can do this

String stringUrl = "https://ipinfo.io/ip";
//String stringUrl = "http://whatismyip.akamai.com/";
// Instantiate the RequestQueue.
RequestQueue queue = Volley.newRequestQueue(MainActivity.instance);
//String url ="http://www.google.com";

// Request a string response from the provided URL.
StringRequest stringRequest = new StringRequest(Request.Method.GET, stringUrl,
        new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {
                // Display the first 500 characters of the response string.
                Log.e(MGLogTag, "GET IP : " + response);

            }
        }, new Response.ErrorListener() {
    @Override
    public void onErrorResponse(VolleyError error) {
        IP = "That didn't work!";
    }
});

// Add the request to the RequestQueue.
queue.add(stringRequest);

This is the easiest and simple way ever exist on the internet... First of all, add this permission to your manifest file...

1. "INTERNET"

2. "ACCESS_NETWORK_STATE"

add this in onCreate file of Activity..

    getPublicIP();

Now Add this function to your MainActivity.class.

    private void getPublicIP() {_x000D_
ArrayList<String> urls=new ArrayList<String>(); //to read each line_x000D_
_x000D_
        new Thread(new Runnable(){_x000D_
            public void run(){_x000D_
                //TextView t; //to show the result, please declare and find it inside onCreate()_x000D_
_x000D_
                try {_x000D_
                    // Create a URL for the desired page_x000D_
                    URL url = new URL("https://api.ipify.org/"); //My text file location_x000D_
                    //First open the connection_x000D_
                    HttpURLConnection conn=(HttpURLConnection) url.openConnection();_x000D_
                    conn.setConnectTimeout(60000); // timing out in a minute_x000D_
_x000D_
                    BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()));_x000D_
_x000D_
                    //t=(TextView)findViewById(R.id.TextView1); // ideally do this in onCreate()_x000D_
                    String str;_x000D_
                    while ((str = in.readLine()) != null) {_x000D_
                        urls.add(str);_x000D_
                    }_x000D_
                    in.close();_x000D_
                } catch (Exception e) {_x000D_
                    Log.d("MyTag",e.toString());_x000D_
                }_x000D_
_x000D_
                //since we are in background thread, to post results we have to go back to ui thread. do the following for that_x000D_
_x000D_
                PermissionsActivity.this.runOnUiThread(new Runnable(){_x000D_
                    public void run(){_x000D_
                        try {_x000D_
                            Toast.makeText(PermissionsActivity.this, "Public IP:"+urls.get(0), Toast.LENGTH_SHORT).show();_x000D_
                        }_x000D_
                        catch (Exception e){_x000D_
                            Toast.makeText(PermissionsActivity.this, "TurnOn wiffi to get public ip", Toast.LENGTH_SHORT).show();_x000D_
                        }_x000D_
                    }_x000D_
                });_x000D_
_x000D_
            }_x000D_
        }).start();_x000D_
_x000D_
    }

Simply use Volley to get the ip from this site

RequestQueue queue = Volley.newRequestQueue(this);    
String urlip = "http://checkip.amazonaws.com/";

    StringRequest stringRequest = new StringRequest(Request.Method.GET, urlip, new Response.Listener<String>() {
        @Override
        public void onResponse(String response) {
            txtIP.setText(response);

        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            txtIP.setText("didnt work");
        }
    });

    queue.add(stringRequest);

Here is kotlin version of @Nilesh and @anargund

  fun getIpAddress(): String {
    var ip = ""
    try {
        val wm = applicationContext.getSystemService(WIFI_SERVICE) as WifiManager
        ip = Formatter.formatIpAddress(wm.connectionInfo.ipAddress)
    } catch (e: java.lang.Exception) {

    }

    if (ip.isEmpty()) {
        try {
            val en = NetworkInterface.getNetworkInterfaces()
            while (en.hasMoreElements()) {
                val networkInterface = en.nextElement()
                val enumIpAddr = networkInterface.inetAddresses
                while (enumIpAddr.hasMoreElements()) {
                    val inetAddress = enumIpAddr.nextElement()
                    if (!inetAddress.isLoopbackAddress && inetAddress is Inet4Address) {
                        val host = inetAddress.getHostAddress()
                        if (host.isNotEmpty()) {
                            ip =  host
                            break;
                        }
                    }
                }

            }
        } catch (e: java.lang.Exception) {

        }
    }

   if (ip.isEmpty())
      ip = "127.0.0.1"
    return ip
}

kotlin minimalist version

fun getIpv4HostAddress(): String {
    NetworkInterface.getNetworkInterfaces()?.toList()?.map { networkInterface ->
        networkInterface.inetAddresses?.toList()?.find {
            !it.isLoopbackAddress && it is Inet4Address
        }?.let { return it.hostAddress }
    }
    return ""
}

If you have a shell ; ifconfig eth0 worked for x86 device too

I don't do Android, but I'd tackle this in a totally different way.

Send a query to Google, something like: https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=my%20ip

And refer to the HTML field where the response is posted. You may also query directly to the source.

Google will most like be there for longer than your Application.

Just remember, it could be that your user does not have internet at this time, what would you like to happen !

Good Luck

You do not need to add permissions like what is the case with the solutions provided so far. Download this website as a string:

http://www.ip-api.com/json

or

http://www.telize.com/geoip

Downloading a website as a string can be done with java code:

http://www.itcuties.com/java/read-url-to-string/

Parse the JSON object like this:

https://stackoverflow.com/a/18998203/1987258

The json attribute "query" or "ip" contains the IP address.

in Kotlin, without Formatter

private fun getIPAddress(useIPv4 : Boolean): String {
    try {
        var interfaces = Collections.list(NetworkInterface.getNetworkInterfaces())
        for (intf in interfaces) {
            var addrs = Collections.list(intf.getInetAddresses());
            for (addr in addrs) {
                if (!addr.isLoopbackAddress()) {
                    var sAddr = addr.getHostAddress();
                    var isIPv4: Boolean
                    isIPv4 = sAddr.indexOf(':')<0
                    if (useIPv4) {
                        if (isIPv4)
                            return sAddr;
                    } else {
                        if (!isIPv4) {
                            var delim = sAddr.indexOf('%') // drop ip6 zone suffix
                            if (delim < 0) {
                                return sAddr.toUpperCase()
                            }
                            else {
                                return sAddr.substring(0, delim).toUpperCase()
                            }
                        }
                    }
                }
            }
        }
    } catch (e: java.lang.Exception) { }
    return ""
}

 //    @NonNull
    public static String getIPAddress() {
        if (TextUtils.isEmpty(deviceIpAddress))
            new PublicIPAddress().execute();
        return deviceIpAddress;
    }

    public static String deviceIpAddress = "";

    public static class PublicIPAddress extends AsyncTask<String, Void, String> {
        InetAddress localhost = null;

        protected String doInBackground(String... urls) {
            try {
                localhost = InetAddress.getLocalHost();
                URL url_name = new URL("http://bot.whatismyipaddress.com");
                BufferedReader sc = new BufferedReader(new InputStreamReader(url_name.openStream()));
                deviceIpAddress = sc.readLine().trim();
            } catch (Exception e) {
                deviceIpAddress = "";
            }
            return deviceIpAddress;
        }

        protected void onPostExecute(String string) {
            Lg.d("deviceIpAddress", string);
        }
    }

private InetAddress getLocalAddress()throws IOException {

            try {
                for (Enumeration<NetworkInterface> en = NetworkInterface.getNetworkInterfaces(); en.hasMoreElements();) {
                    NetworkInterface intf = en.nextElement();
                    for (Enumeration<InetAddress> enumIpAddr = intf.getInetAddresses(); enumIpAddr.hasMoreElements();) {
                        InetAddress inetAddress = enumIpAddr.nextElement();
                        if (!inetAddress.isLoopbackAddress()) {
                            //return inetAddress.getHostAddress().toString();
                            return inetAddress;
                        }
                    }
                }
            } catch (SocketException ex) {
                Log.e("SALMAN", ex.toString());
            }
            return null;
        }

In all honesty I am only a little familiar with code safety, so this may be hack-ish. But for me this is the most versatile way to do it:

package com.my_objects.ip;

import java.net.InetAddress;
import java.net.UnknownHostException;

public class MyIpByHost 
{
  public static void main(String a[])
  {
   try 
    {
      InetAddress host = InetAddress.getByName("nameOfDevice or webAddress");
      System.out.println(host.getHostAddress());
    } 
   catch (UnknownHostException e) 
    {
      e.printStackTrace();
    }
} }

Method getDeviceIpAddress returns device's ip address and prefers wifi interface address if it connected.

  @NonNull
    private String getDeviceIpAddress() {
        String actualConnectedToNetwork = null;
        ConnectivityManager connManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        if (connManager != null) {
            NetworkInfo mWifi = connManager.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
            if (mWifi.isConnected()) {
                actualConnectedToNetwork = getWifiIp();
            }
        }
        if (TextUtils.isEmpty(actualConnectedToNetwork)) {
            actualConnectedToNetwork = getNetworkInterfaceIpAddress();
        }
        if (TextUtils.isEmpty(actualConnectedToNetwork)) {
            actualConnectedToNetwork = "127.0.0.1";
        }
        return actualConnectedToNetwork;
    }

    @Nullable
    private String getWifiIp() {
        final WifiManager mWifiManager = (WifiManager) getApplicationContext().getSystemService(Context.WIFI_SERVICE);
        if (mWifiManager != null && mWifiManager.isWifiEnabled()) {
            int ip = mWifiManager.getConnectionInfo().getIpAddress();
            return (ip & 0xFF) + "." + ((ip >> 8) & 0xFF) + "." + ((ip >> 16) & 0xFF) + "."
                    + ((ip >> 24) & 0xFF);
        }
        return null;
    }


    @Nullable
    public String getNetworkInterfaceIpAddress() {
        try {
            for (Enumeration<NetworkInterface> en = NetworkInterface.getNetworkInterfaces(); en.hasMoreElements(); ) {
                NetworkInterface networkInterface = en.nextElement();
                for (Enumeration<InetAddress> enumIpAddr = networkInterface.getInetAddresses(); enumIpAddr.hasMoreElements(); ) {
                    InetAddress inetAddress = enumIpAddr.nextElement();
                    if (!inetAddress.isLoopbackAddress() && inetAddress instanceof Inet4Address) {
                        String host = inetAddress.getHostAddress();
                        if (!TextUtils.isEmpty(host)) {
                            return host;
                        }
                    }
                }

            }
        } catch (Exception ex) {
            Log.e("IP Address", "getLocalIpAddress", ex);
        }
        return null;
    }

This is a rework of this answer which strips out irrelevant information, adds helpful comments, names variables more clearly, and improves the logic.

Don't forget to include the following permissions:

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

InternetHelper.java:

public class InternetHelper {

    /**
     * Get IP address from first non-localhost interface
     *
     * @param useIPv4 true=return ipv4, false=return ipv6
     * @return address or empty string
     */
    public static String getIPAddress(boolean useIPv4) {
        try {
            List<NetworkInterface> interfaces =
                    Collections.list(NetworkInterface.getNetworkInterfaces());

            for (NetworkInterface interface_ : interfaces) {

                for (InetAddress inetAddress :
                        Collections.list(interface_.getInetAddresses())) {

                    /* a loopback address would be something like 127.0.0.1 (the device
                       itself). we want to return the first non-loopback address. */
                    if (!inetAddress.isLoopbackAddress()) {
                        String ipAddr = inetAddress.getHostAddress();
                        boolean isIPv4 = ipAddr.indexOf(':') < 0;

                        if (isIPv4 && !useIPv4) {
                            continue;
                        }
                        if (useIPv4 && !isIPv4) {
                            int delim = ipAddr.indexOf('%'); // drop ip6 zone suffix
                            ipAddr = delim < 0 ? ipAddr.toUpperCase() :
                                    ipAddr.substring(0, delim).toUpperCase();
                        }
                        return ipAddr;
                    }
                }

            }
        } catch (Exception ignored) { } // if we can't connect, just return empty string
        return "";
    }

    /**
     * Get IPv4 address from first non-localhost interface
     *
     * @return address or empty string
     */
    public static String getIPAddress() {
        return getIPAddress(true);
    }

}

This is my helper util to read IP and MAC addresses. Implementation is pure-java, but I have a comment block in getMACAddress() which could read the value from the special Linux(Android) file. I've run this code only on few devices and Emulator but let me know here if you find weird results.

// AndroidManifest.xml permissions
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

// test functions
Utils.getMACAddress("wlan0");
Utils.getMACAddress("eth0");
Utils.getIPAddress(true); // IPv4
Utils.getIPAddress(false); // IPv6 

Utils.java

import java.io.*;
import java.net.*;
import java.util.*;   
//import org.apache.http.conn.util.InetAddressUtils;

public class Utils {

    /**
     * Convert byte array to hex string
     * @param bytes toConvert
     * @return hexValue
     */
    public static String bytesToHex(byte[] bytes) {
        StringBuilder sbuf = new StringBuilder();
        for(int idx=0; idx < bytes.length; idx++) {
            int intVal = bytes[idx] & 0xff;
            if (intVal < 0x10) sbuf.append("0");
            sbuf.append(Integer.toHexString(intVal).toUpperCase());
        }
        return sbuf.toString();
    }

    /**
     * Get utf8 byte array.
     * @param str which to be converted
     * @return  array of NULL if error was found
     */
    public static byte[] getUTF8Bytes(String str) {
        try { return str.getBytes("UTF-8"); } catch (Exception ex) { return null; }
    }

    /**
     * Load UTF8withBOM or any ansi text file.
     * @param filename which to be converted to string
     * @return String value of File
     * @throws java.io.IOException if error occurs
     */
    public static String loadFileAsString(String filename) throws java.io.IOException {
        final int BUFLEN=1024;
        BufferedInputStream is = new BufferedInputStream(new FileInputStream(filename), BUFLEN);
        try {
            ByteArrayOutputStream baos = new ByteArrayOutputStream(BUFLEN);
            byte[] bytes = new byte[BUFLEN];
            boolean isUTF8=false;
            int read,count=0;           
            while((read=is.read(bytes)) != -1) {
                if (count==0 && bytes[0]==(byte)0xEF && bytes[1]==(byte)0xBB && bytes[2]==(byte)0xBF ) {
                    isUTF8=true;
                    baos.write(bytes, 3, read-3); // drop UTF8 bom marker
                } else {
                    baos.write(bytes, 0, read);
                }
                count+=read;
            }
            return isUTF8 ? new String(baos.toByteArray(), "UTF-8") : new String(baos.toByteArray());
        } finally {
            try{ is.close(); } catch(Exception ignored){} 
        }
    }

    /**
     * Returns MAC address of the given interface name.
     * @param interfaceName eth0, wlan0 or NULL=use first interface 
     * @return  mac address or empty string
     */
    public static String getMACAddress(String interfaceName) {
        try {
            List<NetworkInterface> interfaces = Collections.list(NetworkInterface.getNetworkInterfaces());
            for (NetworkInterface intf : interfaces) {
                if (interfaceName != null) {
                    if (!intf.getName().equalsIgnoreCase(interfaceName)) continue;
                }
                byte[] mac = intf.getHardwareAddress();
                if (mac==null) return "";
                StringBuilder buf = new StringBuilder();
                for (byte aMac : mac) buf.append(String.format("%02X:",aMac));  
                if (buf.length()>0) buf.deleteCharAt(buf.length()-1);
                return buf.toString();
            }
        } catch (Exception ignored) { } // for now eat exceptions
        return "";
        /*try {
            // this is so Linux hack
            return loadFileAsString("/sys/class/net/" +interfaceName + "/address").toUpperCase().trim();
        } catch (IOException ex) {
            return null;
        }*/
    }

    /**
     * Get IP address from first non-localhost interface
     * @param useIPv4   true=return ipv4, false=return ipv6
     * @return  address or empty string
     */
    public static String getIPAddress(boolean useIPv4) {
        try {
            List<NetworkInterface> interfaces = Collections.list(NetworkInterface.getNetworkInterfaces());
            for (NetworkInterface intf : interfaces) {
                List<InetAddress> addrs = Collections.list(intf.getInetAddresses());
                for (InetAddress addr : addrs) {
                    if (!addr.isLoopbackAddress()) {
                        String sAddr = addr.getHostAddress();
                        //boolean isIPv4 = InetAddressUtils.isIPv4Address(sAddr);
                        boolean isIPv4 = sAddr.indexOf(':')<0;

                        if (useIPv4) {
                            if (isIPv4) 
                                return sAddr;
                        } else {
                            if (!isIPv4) {
                                int delim = sAddr.indexOf('%'); // drop ip6 zone suffix
                                return delim<0 ? sAddr.toUpperCase() : sAddr.substring(0, delim).toUpperCase();
                            }
                        }
                    }
                }
            }
        } catch (Exception ignored) { } // for now eat exceptions
        return "";
    }

}

Disclaimer: Ideas and example code to this Utils class came from several SO posts and Google. I have cleaned and merged all examples.

Below code might help you.. Don't forget to add permissions..

public String getLocalIpAddress(){
   try {
       for (Enumeration<NetworkInterface> en = NetworkInterface.getNetworkInterfaces();  
       en.hasMoreElements();) {
       NetworkInterface intf = en.nextElement();
           for (Enumeration<InetAddress> enumIpAddr = intf.getInetAddresses(); enumIpAddr.hasMoreElements();) {
           InetAddress inetAddress = enumIpAddr.nextElement();
                if (!inetAddress.isLoopbackAddress()) {
                return inetAddress.getHostAddress();
                }
           }
       }
       } catch (Exception ex) {
          Log.e("IP Address", ex.toString());
      }
      return null;
}

Add below permission in the manifest file.

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

happy coding!!

In your activity, the following function getIpAddress(context) returns the phone's IP address:

public static String getIpAddress(Context context) {
    WifiManager wifiManager = (WifiManager) context.getApplicationContext()
                .getSystemService(WIFI_SERVICE);

    String ipAddress = intToInetAddress(wifiManager.getDhcpInfo().ipAddress).toString();

    ipAddress = ipAddress.substring(1);

    return ipAddress;
}

public static InetAddress intToInetAddress(int hostAddress) {
    byte[] addressBytes = { (byte)(0xff & hostAddress),
                (byte)(0xff & (hostAddress >> 8)),
                (byte)(0xff & (hostAddress >> 16)),
                (byte)(0xff & (hostAddress >> 24)) };

    try {
        return InetAddress.getByAddress(addressBytes);
    } catch (UnknownHostException e) {
        throw new AssertionError();
    }
}

WifiManager wm = (WifiManager) getSystemService(WIFI_SERVICE);
String ipAddress = BigInteger.valueOf(wm.getDhcpInfo().netmask).toString();

Please check this code...Using this code. we will get ip from mobile internet...

for (Enumeration<NetworkInterface> en = NetworkInterface.getNetworkInterfaces(); en.hasMoreElements(); ) {
                NetworkInterface intf = en.nextElement();
                for (Enumeration<InetAddress> enumIpAddr = intf.getInetAddresses(); enumIpAddr.hasMoreElements(); ) {
                    InetAddress inetAddress = enumIpAddr.nextElement();
                    if (!inetAddress.isLoopbackAddress()) {
                        return inetAddress.getHostAddress().toString();
                    }
                }
            }

A device might have several IP addresses, and the one in use in a particular app might not be the IP that servers receiving the request will see. Indeed, some users use a VPN or a proxy such as Cloudflare Warp.

If your purpose is to get the IP address as shown by servers that receive requests from your device, then the best is to query an IP geolocation service such as Ipregistry (disclaimer: I work for the company) with its Java client:

https://github.com/ipregistry/ipregistry-java

IpregistryClient client = new IpregistryClient("tryout");
RequesterIpInfo requesterIpInfo = client.lookup();
requesterIpInfo.getIp();

In addition to being really simple to use, you get additional information such as country, language, currency, the time zone for the device IP and you can identify whether the user is using a proxy.

Based on what I have tested this is my proposal

import java.net.*;
import java.util.*;

public class hostUtil
{
   public static String HOST_NAME = null;
   public static String HOST_IPADDRESS = null;

   public static String getThisHostName ()
   {
      if (HOST_NAME == null) obtainHostInfo ();
      return HOST_NAME;
   }

   public static String getThisIpAddress ()
   {
      if (HOST_IPADDRESS == null) obtainHostInfo ();
      return HOST_IPADDRESS;
   }

   protected static void obtainHostInfo ()
   {
      HOST_IPADDRESS = "127.0.0.1";
      HOST_NAME = "localhost";

      try
      {
         InetAddress primera = InetAddress.getLocalHost();
         String hostname = InetAddress.getLocalHost().getHostName ();

         if (!primera.isLoopbackAddress () &&
             !hostname.equalsIgnoreCase ("localhost") &&
              primera.getHostAddress ().indexOf (':') == -1)
         {
            // Got it without delay!!
            HOST_IPADDRESS = primera.getHostAddress ();
            HOST_NAME = hostname;
            //System.out.println ("First try! " + HOST_NAME + " IP " + HOST_IPADDRESS);
            return;
         }
         for (Enumeration<NetworkInterface> netArr = NetworkInterface.getNetworkInterfaces(); netArr.hasMoreElements();)
         {
            NetworkInterface netInte = netArr.nextElement ();
            for (Enumeration<InetAddress> addArr = netInte.getInetAddresses (); addArr.hasMoreElements ();)
            {
               InetAddress laAdd = addArr.nextElement ();
               String ipstring = laAdd.getHostAddress ();
               String hostName = laAdd.getHostName ();

               if (laAdd.isLoopbackAddress()) continue;
               if (hostName.equalsIgnoreCase ("localhost")) continue;
               if (ipstring.indexOf (':') >= 0) continue;

               HOST_IPADDRESS = ipstring;
               HOST_NAME = hostName;
               break;
            }
         }
      } catch (Exception ex) {}
   }
}