Java code to listing Network Interface Addresses run on Windows 10

One of the most useful pieces of information you can get from a network interface is the list of IP addresses that are assigned to it. You can obtain this information from a NetworkInterface instance by using one of two methods. The first method, getInetAddresses(), returns an Enumeration of InetAddress. The other method, getInterfaceAddresses(), returns a list of java.net.InterfaceAddress instances. This method is used when you need more information about an interface address beyond its IP address. For example, you might need additional information about the subnet mask and broadcast address when the address is an IPv4 address, and a network prefix length in the case of an IPv6 address. ~ https://docs.oracle.com/javase/tutorial/networking/nifs/listing.html

The following example program lists all the network interfaces and their addresses on a machine (tested on PC running Windows 10):

package javalistinetaddress;

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

public class JavaListInetAddress {

 public static void main(String[] args) throws SocketException {
 Enumeration<NetworkInterface> nets = NetworkInterface.getNetworkInterfaces();
 for (NetworkInterface netint : Collections.list(nets))
 displayInterfaceInformation(netint);
 }
 
 static void displayInterfaceInformation(NetworkInterface netint) throws SocketException {
 System.out.printf("Display name: %s ", netint.getDisplayName());
 System.out.printf("Name: %s ", netint.getName());
 Enumeration<InetAddress> inetAddresses = netint.getInetAddresses();
 for (InetAddress inetAddress : Collections.list(inetAddresses)) {
 System.out.printf("InetAddress: %s ", inetAddress);
 }
 System.out.printf(" ");
 }
 
}

Related:
- Java code to listing Network Interface Addresses, run on Raspberry Pi/Raspbian Jessie

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Retrieve IP and MAC addresses from proc net arp

Last post "Display WiFi Hotspot clients by "cat /proc/net/arp"" display arp as human readable string, but not machine readable. Its another version to retrieve IP and MAC addresses, store in a ArrayList.

MainActivity.java

package com.blogspot.android_er.androidlistclient;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

 Button btnRead;
 TextView textResult;

 ArrayList<Node> listNote;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 btnRead = (Button)findViewById(R.id.readclient);
 textResult = (TextView)findViewById(R.id.result);

 listNote = new ArrayList<>();

 btnRead.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 readAddresses();
 textResult.setText("");
 for(int i=0; i<listNote.size(); i++){
 textResult.append(i + " ");
 textResult.append(listNote.get(i).toString());
 textResult.append(" ");
 }
 }
 });
 }

 private void readAddresses() {
 listNote.clear();
 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("..:..:..:..:..:..")) {
 Node thisNode = new Node(ip, mac);
 listNote.add(thisNode);
 }
 }
 }

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

 class Node {
 String ip;
 String mac;

 Node(String ip, String mac){
 this.ip = ip;
 this.mac = mac;
 }

 @Override
 public String toString() {
 return ip + " " + mac;
 }
 }
}

layout/activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 
 
 android_layout_width="match_parent"
 android_layout_height="match_parent"
 android_padding="16dp"
 android_orientation="vertical"
 tools_context="com.blogspot.android_er.androidlistclient.MainActivity">

 <TextView
 android_layout_width="wrap_content"
 android_layout_height="wrap_content"
 android_layout_gravity="center_horizontal"
 android_autoLink="web"
 android_text="http://android-er.blogspot.com/"
 android_textStyle="bold" />

 <Button
 android_id="@+id/readclient"
 android_layout_width="match_parent"
 android_layout_height="wrap_content"
 android_textAllCaps="false"
 android_text="Read Ip/MAC addresses"/>

 <TextView
 android_id="@+id/result"
 android_layout_width="match_parent"
 android_layout_height="wrap_content"
 android_typeface="monospace"
 android_textSize="24sp"/>
</LinearLayout>

Next:
- Lookup manufacturer info by MAC address, using www.macvendorlookup.com API
- Get HostName of WiFi hotspot clients, and check if it is still connected

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