Applet design help needed...

Question

Hello and thank you if you decide to reply to this post. I am a former C++ programmer (intermediate level) jumping head-first into Java.
The first project I have made for myself is a web-based gui packet sniffer. Here is the physical setup: I have a Linux box on my network running a packet sniffing program (tcpdump for those interested) and a web server (apache, again for those interested).
I would like to write a Java program on the Linux box that would redirect the packet sniffing program's output to a webpage viewable on the internet (and my internal network).
At first, I wrote an applet to redirect the output to a webpage but could not view it over my internal network. I thought maybe I needed to write a client and server program that creates sockets to pass information over the network (and internet), but I have been to webpages that display realtime output in text and graphical form without using special clientside code.
I guess I am saying is that I know this can be done, but I'm not sure how to do it.

Answer 1

tcpdump can write to the screen of the computer it is running on (standard output) or to a file in realtime. Have you ever opened a console to ping a host like: "ping www.yahoo.com"? You'll get an ICMP reply like: "Reply from 64.58.76.227: bytes=32 time=50ms TTL=236" In case you didn't know, 'ping' is a simple program that uses a sub protocol of TCP/IP (the protocol of the internet) called ICMP to send a request to a given machine and listen for a reply. Once it recieves the reply, it prints it to the screen and says how big the message sent was (in the above case 32 bytes) how long it took to get there (in the above case 50 milliseconds) and how long ping should wait intil it should declare the target (in the above case www.yahoo.com) as a 'Request timed out'. This wait period is called a Time To Live or TTL (in the above case 236 milliseconds)
Now imagine information like this, but for ALL the data traffic coming in and out of a certain network card on the computer running tcpdump. This information scrolls on the screen, or to a file, about as fast as you can scroll through a full text document. Of course there are arguments to tcpdump to request more or less or specific information about data packets traveling to the host machine.
Simply put, what I would like is the ability to open a webpage (residing on and being served from the same machine running tcpdump) and see tcpdump's output as if I were looking at the monitor of the computer it is running on. Also, I would like to be able to open this webpage from anywhere on my network or on the internet.
I know how to serve webpages to the internet or to a network, the problem is writing Java code to output it to the webpage. Later I plan to make graphs of network bandwith usage or protocol frequency, but for now I am just trying to figure out how to direct tcpdump's output to a webpage and view it in realtime.
So far, I have written code (with the help of the GREAT Forum community here) that executes tcpdump, redirects the standard output to BufferedReadert and then prints that BufferedReader to the screen. Here is the code:
public class tcpdumpReadOutputNonApplet
public static void main(String args[])
     try
          Process tcpdump = Runtime.getRuntime().exec("/usr/sbin/tcpdump -l -i any");
          System.out.println("PROCESS STARTED...");
          BufferedReader in = new BufferedReader(new InputStreamReader(tcpdump.getInputStream()));
          System.out.println("STREAM READ INTO BUFFER...");
          String tcpdumpStream;
          while ((tcpdumpStream = in.readLine()) != null)
          {       //print the output to screen
               System.out.println(tcpdumpStream);
          }//end while
     }//end try
     catch (Exception e)
          String error = e.toString();
          System.out.println("EXCEPTION OCCURED!");
          System.out.println(error);
}//end main()
}//tcpdumpReadOutput()
Once I got that to work, my next step was to try to redirect the BufferedReader to print to a webpage, but it didn't work. I thought (perhaps foolishly) that all I had to do was change this application into an applet and replace System.out.println with a drawString meathod. Well it didn't work. At least over my internal network. Something I might add is that the webpage I tried this on was not being served thru a webserver. It was just an HTML file that was opened over the network. Maybe this has something to do with it but I am doubtful.
So that is my dilemma. Hope this post isn't too painful to read ^_^