Question

Use the firewall-cmd to drop all incoming pings.

Try to ping your CentOS machine from your Mac. It should not work.

Write down the command

Remove the previous rule created (the one from question 1)

Write down the command

Answer 1

import java.io.BufferedReader;
	import java.io.InputStreamReader;
	public class PingIP {
	public static void runSystemCommand(String command) {
	try {
	Process p = Runtime.getRuntime().exec(command);
	BufferedReader inputStream = new BufferedReader(
	new InputStreamReader(p.getInputStream()));
	String s = "";
	// reading output stream of the command
	while ((s = inputStream.readLine()) != null) {
	System.out.println(s);
	}
	} catch (Exception e) {
	e.printStackTrace();
	}
	}
	public static void main(String[] args) {
	String ip = "google.com";
	runSystemCommand("ping " + ip);
	}
	}