A Java PL/SQL Port Scanner

Saturday night I started to wonder how I could get the movies of my DVR. Recently Verizon FIOS added a boatload of HD stations so I've naturally begun to record those. Problem is, the 50 hours or so I have available are quickly eaten up by the HD versions.

We have the multi-room DVR setup, which means we have one DVR but we can view those movies from any TV (with a cable box). Naturally all these boxes are on my internal network (router provided by Verizon).

I understand that with some boxes you can go out and buy additional storage, but I wanted a DIY solution. So, if I could find an open port on one of these boxes, then perhaps I could figure out a way to get the movies onto my computer.

Java to the rescue. Well, not really, but I have always wanted to learn more about that kind of lower level programming (sockets/ports/TCP/whatever). See, I don't really know what I'm talking about which is why I did it.

Since I use JDeveloper for writing SQL and PL/SQL, creating a java class (with the Main method) is easy.

import java.io.IOException;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.Date;

public class Class1
{
  private static void p ( String text )
  {
    System.out.println( text );
  }

  public static void main(String[] args) throws UnknownHostException, IOException
  {
    Date startDate = new Date();
    String machine = "192.168.1.102";
    Thread thread = new Thread();

    Socket socket;
    int j = 0;
    int x = 0;
    p( "start date/time:  " + startDate.toString() );
    for ( int i = 1000; i < 10000; i++ )
    {
      x++;
      p( "checking port:  " + machine + ":" + i );
      try
      {
        socket = new Socket( machine, i );
        p( "Port open:  " + machine + ":" + i );
        j++;
      }
      catch (UnknownHostException e) { }
      catch (IOException e) { }
      finally
      {
      }
    }
    p( "ports checked:  " + x );
    p( "ports open:  " + j );
    p( "start date/time:  " + startDate.toString() );
    p( "end date/time:    " + new Date().toString() );
  }
}

As LC would say, "That's not so bad."

Only it was slow, 1 port at a time. I did learn that trying to open up a port connection is s l o w. How can I speed this up?

I could make it threaded right? No. That would take too much time.

But hey, I know how to do it in PL/SQL (threaded that is). UTL_TCP should work nicely. I've never had to use it, so a great opportunity to familiarize myself with it (not that it's needed very often).

So I start Oracle XE and initially just try it out to see how it works:

DECLARE
  c UTL_TCP.CONNECTION;
BEGIN
  c := utl_tcp.open_connection
        ( remote_host => '192.168.1.2',
          remote_port => 1,
          tx_timeout => 1 );
  
  utl_tcp.close_connection( c );
EXCEPTION
  WHEN others THEN
    utl_tcp.close_connection( c );
END check_port;
/

Easy enough. Now let's start use DBMS_JOB to "thread" this.

DECLARE
  TYPE r_record IS TABLE OF OPEN_PORTS.IP%TYPE INDEX BY BINARY_INTEGER;
  l_table R_RECORD;
  job_count PLS_INTEGER;
  job_number PLS_INTEGER;
BEGIN
  l_table(1) := '192.168.1.102';
  
  FOR i IN 1..l_table.COUNT LOOP
    FOR j IN 1..10000 LOOP
      SELECT COUNT(*)
      INTO job_count
      FROM user_jobs;

      WHILE job_count < 20 LOOP
      
        dbms_job.submit
          ( job => job_number,
            what => 'BEGIN check_port( ''' || l_table(i) || ''',' || j || '); COMMIT; END;' );

        COMMIT;
      END LOOP;
    END LOOP;    
  END LOOP;
END;
/

So it's running, and running, and running...I opened up another session and did a count on user_jobs. 10000. 12000. 20000. Uh, I think there's something wrong here.

I finally kill the session and there are 36,446 jobs in the queue. All checking the same port.

Then I can't even issue a simple SELECT statement. Maximum number of sessions reached or some such rubbish. Just a reminder, it was Saturday night and I was just trying to see if I could do this quickly.

Since I couldn't connect, I tried bouncing the database (a loud gasp from the DBAs out there). Come on! It's a local XE instance...there's nothing important there.

Start it back up, connect as SYS and still can't issue any queries. I do notice as I hit the / sign and the Enter key a bunch of times that once in a while it will let me do a query. So I create a quick PL/SQL block to remove all the jobs from the queue.

BEGIN
  FOR i IN ( SELECT job FROM user_jobs ) LOOP
    dbms_job.remove( i.job );
  END LOOP;
END;
/

I go through the / + Enter key about 50 times until it finally runs. Success!

Or so I think. Still receiving the max sessions error. There are still 36,446 jobs in user_jobs. I can't remove them anymore as I get "job doesn't exist" when I try to dbms_job.remove it again. Hmmm...How about?

DELETE FROM dba_jobs;

36,446 rows deleted.

What?

How can that be? I didn't expect that to work at all...but it did. I have yet to look up the particulars of my actions (deleting from dba_jobs) but it did the job.

And yes, I'm still planning on writing this (correctly) in the near future...I want more movies!