extract a hardware MAC address from a given IP address using the ARP cache (/proc/net/arp). - Android java.net

Android examples for java.net:IP Address

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Description

extract a hardware MAC address from a given IP address using the ARP cache (/proc/net/arp).

Demo Code

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class Main {

  /**/*from   ww  w . j  ava 2s  .  c  o  m*/
   * Try to extract a hardware MAC address from a given 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 the MAC from the ARP cache
   */
  public static String getMacFromArpCache(String ip) {
    if (ip == null)
      return null;
    BufferedReader br = null;
    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 && ip.equals(splitted[0])) {
          // Basic sanity check
          String mac = splitted[3];
          if (mac.matches("..:..:..:..:..:..")) {
            return mac;
          } else {
            return null;
          }
        }
      }
    } catch (Exception e) {
      e.printStackTrace();
    } finally {
      try {
        br.close();
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
    return null;
  }

  public static String getMacFromArpCache(int ip) {
    byte[] i = new byte[4];
    i[0] = (byte) ((byte) ip & 0xff);
    i[1] = (byte) ((byte) (ip >> 8) & 0xff);
    i[2] = (byte) ((byte) (ip >> 16) & 0xff);
    i[3] = (byte) ((byte) (ip >> 24) & 0xff);
    String ipString = String.format("%d.%d.%d.%d", i[0], i[1], i[2], i[3]);
    return getMacFromArpCache(ipString);
  }
}

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