Scan Reachable IP to discover devices in network

This example, scan a range of IPs, to check if it is reachable, in turn to discover connected devices in the same network.

MainActivity.java

package com.blogspot.android_er.androidipscanner;

import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;

import java.io.IOException;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

 private Button btnScan;
 private ListView listViewIp;

 ArrayList<String> ipList;
 ArrayAdapter<String> adapter;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 btnScan = (Button)findViewById(R.id.scan);
 listViewIp = (ListView)findViewById(R.id.listviewip);


 ipList = new ArrayList();
 adapter = new ArrayAdapter<String>(this,
 android.R.layout.simple_list_item_1, android.R.id.text1, ipList);
 listViewIp.setAdapter(adapter);

 btnScan.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 new ScanIpTask().execute();
 }
 });

 }

 private class ScanIpTask extends AsyncTask<Void, String, Void>{

 /*
 Scan IP 192.168.1.100~192.168.1.110
 you should try different timeout for your network/devices
 */
 static final String subnet = "192.168.1.";
 static final int lower = 100;
 static final int upper = 110;
 static final int timeout = 5000;

 @Override
 protected void onPreExecute() {
 ipList.clear();
 adapter.notifyDataSetInvalidated();
 Toast.makeText(MainActivity.this, "Scan IP...", Toast.LENGTH_LONG).show();
 }

 @Override
 protected Void doInBackground(Void... params) {

 for (int i = lower; i <= upper; i++) {
 String host = subnet + i;

 try {
 InetAddress inetAddress = InetAddress.getByName(host);
 if (inetAddress.isReachable(timeout)){
 publishProgress(inetAddress.toString());
 }

 } catch (UnknownHostException e) {
 e.printStackTrace();
 } catch (IOException e) {
 e.printStackTrace();
 }
 }

 return null;
 }

 @Override
 protected void onProgressUpdate(String... values) {
 ipList.add(values[0]);
 adapter.notifyDataSetInvalidated();
 Toast.makeText(MainActivity.this, values[0], Toast.LENGTH_LONG).show();
 }

 @Override
 protected void onPostExecute(Void aVoid) {
 Toast.makeText(MainActivity.this, "Done", Toast.LENGTH_LONG).show();
 }
 }

}

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=".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/scan"
 android_layout_width="match_parent"
 android_layout_height="wrap_content"
 android_text="Scan"/>
 <ListView
 android_id="@+id/listviewip"
 android_layout_width="match_parent"
 android_layout_height="wrap_content"/>
</LinearLayout>

Permission of "android.permission.INTERNET" is needed in AndroidManifest.xml

 <uses-permission android_name="android.permission.INTERNET"/>

---

Related:
- Java version run on Raspberry Pi - scan connected IP in the same network

Read More..

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

Read More..