ICMP ECHO

public static boolean isReachableByPing(String host) {
        try{
                String cmd = "";                if(System.getProperty("os.name").startsWith("Windows")) {  
                        // For Windows
                        cmd = "ping -n 1 " + host;
                } else {
                        // For Linux and OSX
                        cmd = "ping -c 1 " + host;
                }
                Process myProcess = Runtime.getRuntime().exec(cmd);
                myProcess.waitFor();
                if(myProcess.exitValue() == 0) {
                        return true;
                } else {
                        return false;
                }
        } catch( Exception e ) {
                e.printStackTrace();
                return false;
        }