Android Open Source - chaski Connections Cache Helper

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License

The source code is released under:

Apache License

Java Source Code

package chaski.api.util.networking;
//from   w w w  . jav  a2s.co  m
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;

import android.util.Log;

public class ConnectionsCacheHelper {
  
  
  public final static String TAG =  ConnectionsCacheHelper.class.getName();
  
  private final static int TIMEOUT = 2000;

  /**
      * Try to extract IP address using the ARP cache (/proc/net/arp).<br>
      * <br>
      * We assume that the file has this structure:<br>
      * <br>
      * IP address       HW type     Flags       HW address            Mask     Device
      * 192.168.18.11    0x1         0x2         00:04:20:06:55:1a     *        eth0
      * 192.168.18.36    0x1         0x2         00:22:43:ab:2a:5b     *        eth0
      *
      * @param ip
      * @return a list containing all registered IP addresses in the ARP cache
      */
     public List <String> extractIPs() {
          
         BufferedReader br = null;
         
         
         List <String> extractedIpList = new CopyOnWriteArrayList
             <String>();
         try {
             br = new BufferedReader(new FileReader("/proc/net/arp"));
             String line;
             while ((line = br.readLine()) != null) {
                
               String[] splitted = line.split(" +");
                 if (splitted != null && splitted.length >= 4 && !splitted[0].startsWith("IP")) {
                     // Basic sanity check
                     String ip = splitted[0];
                     if (ip!=null && !ip.isEmpty()) {
                         extractedIpList.add(ip);
                     } else {
                         return null;
                     }
                 }
             }
             
             
         } 
         catch (FileNotFoundException e) {
          Log.e(TAG, "Problem reading file to get connected devices.");  
        }
         catch (IOException e) {
           Log.e(TAG, "Problem reading a line to get connected devices.");
         } finally {
             try {
                 br.close();
             } catch (IOException e) {
               Log.e(TAG, "Problem closing buffered reader.");
             }
         }
         
         return extractedIpList;
     }

  
     public boolean canReachAtLeastOneClient(){
       
       List<String> ipList = getListOfValidClients();
       
       boolean val = false;
       
       
       for(String ip : ipList){
         
         val = isReachable(ip);
         
         if(val){
           return true;
         }
       }
       
       return val;
     }
     
     public List <String> getListOfValidClients(){
       
         List<String> ipList = extractIPs();
         
         boolean val = false;
         
         
         for(String ip : ipList){
           
           val = isReachable(ip);
           
           if(!val){ 
             //client not reachable => remove it from list 
             ipList.remove(ip);
           }
         }
         
         return ipList;
      
     }


    private boolean isReachable(String host) {
        
           
           
           InetAddress[] addresses;
        try {
          addresses = InetAddress.getAllByName(host);
          
          for (InetAddress address : addresses)
             { 
                 if ( address.isReachable(TIMEOUT))
                 {
                    return true; // just set a break point here
                 }
             }
             
        } catch (UnknownHostException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
        } catch (IOException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
        } 
           
           return false;
      }
  
     
  
}

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