isReachable() method for ping measurements returns wrong value

Question

I'm trying to use Java's isReachable() method to measure ping latency between my pc and a server. By far I've been using this method:

 Process p1 = Runtime.getRuntime().exec("ping -n 1 " + indIP);
    int pingValue = 0;

    long t1 = System.currentTimeMillis();
    try {

        p1.waitFor();

    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    long t2 = System.currentTimeMillis();


    int exit = p1.exitValue();
    if (exit==0){
        pingValue = (int) (t2-t1);
        return pingValue;
    }
    else
        return -1;

but I noticed that it returned a value higher than the ping value got by using CMD (approx +10ms).

So I tried to use the method provided by InetAddress, but the value seems completely wrong.

Here's the code:

 String servername = "xx.xx.xx.xx";

    InetAddress addr = InetAddress.getByName(servername);
    long currentTime = System.currentTimeMillis();
    boolean pingOK = addr.isReachable(2000);
    currentTime = System.currentTimeMillis() - currentTime;
    if(pingOK) {
        System.out.println("Ping: "+ currentTime+ " ms");
    } else {
        System.out.println("Ping failed.");
    }

If I try, for example, to ping a server via CMD i get 9-10ms, but this method returns a value 100 times higher for the same server or it does not work at all. I gave a look at other threads here on Stackoverflow, but I couldn't find anything to get my ping check more accurate.

Thanks in advance for your time.

EDIT: I got a more accurate value by defining another method to "measure" the system latency:

public static int getSysLatency() throws IOException{
     long t3 = System.currentTimeMillis();

        Process p2 = Runtime.getRuntime().exec("ping -n 1 127.0.0.1");

        try {
            p2.waitFor();
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        t3 = System.currentTimeMillis()-t3;

        return (int) t3;
}

The latency in this case should be <1ms, so I can get the system "delay" when Process p1 = Runtime.getRuntime().exec("ping -n 1 " + indIP); is called.

Then I subtracted t3 to pingValue and I got a better latency value, that is almost the same displayed via CMD.

isReachable() method for ping measurements returns wrong value

0 Answers0