How can I share Perl data structures through a socket?

Question

In sockets I have written the client server program. First I tried to send the normal string among them it sends fine. After that I tried to send the hash and array values from client to server and server to client. When I print the values using Dumper, it gives me only the reference value. What should I do to get the actual values in client server?

Server Program:

use IO::Socket;
use strict;
use warnings;

my %hash = ( "name" => "pavunkumar " , "age" => 20 ) ;
my $new  = \%hash ;
#Turn on System variable for Buffering output
$| = 1;
# Creating a a new socket
my $socket=
IO::Socket::INET->new(LocalPort=>5000,Proto=>'tcp',Localhost =>
        'localhost','Listen' => 5 , 'Reuse' => 1 );
die "could not create $! \n" unless ( $socket );
        print "\nUDPServer Waiting port 5000\n";
        my $new_sock =  $socket->accept();
        my $host =  $new_sock->peerhost();
        while(<$new_sock>)
        {
        #my $line = <$new_sock>;
        print Dumper "$host $_";
        print $new_sock $new . "\n";
        }
        print "$host is closed \n" ;

Client Program

use IO::Socket;                               
use Data::Dumper ;                            
use warnings ;                                
use strict ;                                  

my %hash  = ( "file" =>"log.txt" , size => "1000kb") ;

my $ref = \%hash ;


# This client for connecting the specified below address and port 
# INET function will create the socket file and establish the connection with
# server

my $port = shift || 5000 ;
my $host = shift || 'localhost';
my $recv_data ;
my $send_data;
my $socket = new IO::Socket::INET (
                                  PeerAddr  => $host ,
                                  PeerPort  => $port ,
                                  Proto => 'tcp', )

or die "Couldn't connect to Server\n";
while (1)
{
        my $line = <stdin> ;
        print $socket $ref."\n";
        if ( $line = <$socket> )
        {
                print Dumper  $line ;
        }
        else
        {
                print "Server is closed \n";
                last ;
        }

}

I have given my sample program about what I am doing. Can any one tell me what I am doing wrong in this code? And what I need to do for accessing the hash values?

Answer 1

Problem is you are sending references to the data, not the data itself. You need to serialize the data somehow. JSON is a very easy way to do that. There is also YAML.

Answer 2

When you say

print $ref;

, you're in part instructing Perl to turn $ref into a string (since only strings can be printed). It turns out that references don't turn into very useful strings by default.

You need to turn $ref into a string that you can send across the wire and then decode on the other side to get the data back out. This process is referred to as "serialization". Data::Dumper's output is actually a valid serialization of its arguments, but the basic serialization module in Perl is Storable.

Procedurally, you can say[1]

use Storable qw(nfreeze); # nfreeze rather than freeze because
                          # we want a network-portable string
...
print nfreeze($ref);

on one side and

use Storable qw(thaw);
...
my $ref = thaw($line);

on the other.

There's also an OO interface; read the Storable documentation for more information.

[1]: Notice the yaddayaddas. This is incomplete code that merely illustrates the key differences from your code.