When you attempt to read data in your server, you are attempting to read a 'line':

while(defined(my $data=<$client_socket>))
[download]

But when your client writes the data, it doesn't add any delimiter:

        print $socket $data[$_];
[download]

You need to read the docs and understand how Perl's basic IO functions work.

And whilst we're at it, what on earth is your reasoning for first joining a bunch of variables together with spaces, and then spliting them apart again?

    # write on the socket to server.
    $_=join(' ',$status,$md,$md_others);
    @data=split(" ",$_);
[download]