MacAddress.java

package io.evercam.network.discovery;

import io.evercam.network.Constants;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class MacAddress {

    /**
     * Read hardware address from ARP table by specified IP address(work for
     * Android only). If no MAC address associated, return 00:00:00:00:00:00.
     * 
     * @param ip
     *            host IP address
     */
    public static String getByIpLinux(String ip) {
	final String MAC_RE = "^%s\\s+0x1\\s+0x2\\s+([:0-9a-fA-F]+)\\s+\\*\\s+\\w+$";
	final int BUF = 8 * 1024;
	String hw = Constants.EMPTY_MAC;
	try {
	    if (ip != null) {
		String ptrn = String.format(MAC_RE, ip.replace(".", "\\."));
		Pattern pattern = Pattern.compile(ptrn);
		BufferedReader bufferedReader = new BufferedReader(
			new FileReader("/proc/net/arp"), BUF);
		String line;

		Matcher matcher;
		while ((line = bufferedReader.readLine()) != null) {
		    matcher = pattern.matcher(line);
		    if (matcher.matches()) {
			hw = matcher.group(1);
			break;
		    }
		}
		bufferedReader.close();
	    }
	} catch (IOException e) {
	    return hw;
	}
	return hw;
    }
}