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

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