Thanks again. I've never taken the time to learn how pack and unpack work as well as I should, and it looks like that mistake has finally caught up with me.

For what it's worth - the original C++ code (which I didn't write) used the functions htonl() and ntohl(). I was not familiar with those, but could tell that it had something to do with encoding/decoding data, so I googled for a perl implementation, and found one in the Net::Inet module on CPAN. It's written to take an array of inputs, but I knew that in my case I'd only be sending in a single argument.

As it turns out, my code did have another error: recv() returns undef if there's an error, so I had to change this:

# this is broken !!!
$socket->recv($data, $reponse_length) or die "Couldn't read data from 
+server: $!";
[download]

into this:

unless (defined $socket->recv($data, $reponse_length)) {
  die "Couldn't read data from server: $!";
}
[download]

But everything seems to be working now -thank you!!