Creating an Network IP tool

Question

Hi, I just have a few questions. I run a couple computer labs and they all are on the same subnet (ex. 202.128.34.1), and all the computers have unique static IP addresses (ex. 202.128.34.34). Many times I forget what IP addresses I have already assigned. I would like to create a Java app that I could use to possibly ping every IP address for a given subnet, and then the app will return the results of the pings and can tell me which IP addresses are currently in use, and which ones are not. I would like to know what tools are available for such a program, or possibly a way I could get started.

Answer 1

Okay got the basics out of the way, now I have created a gui, rather than post the entire code, I will just give you an update. I created a JFrame with one JButton, and one JTextArea. I have placed the code for the actionPerformed below:
fourthIPBytes[ ] equals {"1", "2", "3", "4"}, and ipAddressTextArea is the JTextArea that appends the IP addresses that are in use.
This is how the program works. You click the button, and then it starts the actionPerformed and does the following. I just have one problem. Rather than add the IP addresses to the JTextArea after each test they dont. The program writes to the console after each IP test automatically, but the JTextArea doesnt actually get updated until after the entire for loop is completed. I tried using validate() after each test but the gui doesnt show the used IP addresses until after its all done. What needs to be done so that the gui places the IP addresses that are in use on the JTextArea right away, insted of having to wait until the entire for loop is done? I hope I have explained this right.
public void actionPerformed(ActionEvent aEvent)
        try
            InetAddress ia = null;
            for(int i = 0; i < 5; i++)
                ia = InetAddress.getByName("202.128.34." + fourthIPBytes);
try
if(ia.isReachable(2000))
System.out.println("202.128.34." + fourthIPBytes[i] + " is in use");
ipAddressTextArea.append("202.128.34."+ fourthIPBytes[i]);
ipAddressTextArea.append("\n");
else
System.out.println("202.128.34."+ fourthIPBytes[i] + " is available");
catch(IOException ee) {}
catch(UnknownHostException e) {}