Hierarchical data in a relational database

Hi All

Today an interesting article about how represents hierarchical data in a relational database.

 http://fungus.teststation.com/~jon/treehandling/TreeHandling.htm

Interesting this concept :

Every node must have a node identify and a "Child of" identify. So the key of every object is formed by two keys :

• ID_NODE
• CHILD_OF

For example (represents image above) :

ID_NODE  CHILD_OF
1	1
2	1
3	1
4	2
5	3
6	5

Stay tuned.

How To Identify If a Port Is Listening on a Unix Server

Hi all

To see if a port is listening on a Unix Server command is :

           netstat -an | grep port number | grep LISTEN

To see what process is using a port the command is :

           lsof -i tcp:port number

Here a simple perl programm to open a port and check a connection from a client web :


#!/usr/bin/perl -w
        use IO::Socket;
        use Net::hostent;              # for OO version of gethostbyaddr
        $PORT = 8080;

        $server = IO::Socket::INET->new( Proto     => 'tcp',
                                         LocalPort => $PORT,
                                         Listen    => 5,
                                         Reuse     => 1) or die "can't setup server" unless $server;

    printf("\nSERVER Waiting for client connection on port $PORT");

         while ($client = $server->accept()) {

          printf("\nClient Connected\n");

          $client->autoflush(1);
          print $client " You are connected on port $PORT";

          close $client;
        }

Stay tuned