Hello, everyone.

I have been searching for a solution to my problem through lots of forums and resources before I write this post, but this is my last chance to solve it. I tell you:

I have connected a pc with a laptop via a serial null cable modem, following the instructions provided in a howto I found, with the ppp protocol. Even I can get a connection to internet in the laptop through the pc, as in a LAN. Then I wrote a little program in Perl, that uses IO::Socket::INET, for transferring data from one computer to another. The pc works as server and the laptop as client. The goal of the program is control the pc from the laptop sending and receiving data from this one to the other, navigate through server directories and import/export files between the two machines giving orders from the laptop. I have tested the program in a real LAN with two pc's working with windows 95 and 98, ethernet cards and ActivePerl 5.8 and it works fine. The pc's are a Pentium II at 233 Mhz and 128 Mgs and a Pentium III at 800 Mhz and 256 Mgs. The problem I have is:

For trasferring a file from the server to the client, I divide the file into little parts, and I put them on an array. Then I send this parts with
$Socket->send($part); And in the client I do $Socket->recv($part,1024). When all the parts are received, I group and write them into the new file.
It works in a terminal. Well, when I'm receiving data and I open another terminal for execute anything else, or when the screen of the laptop gets off (I don't know if it's well explained, my english is a little poor yet), then the conexion halts. No messages, no errors are displayed, and I have put some signals and outputs to locate the problem. No nothing. Just the transfer stops in both the server and the client. I have included alarms so if in a few seconds one of them doesn't receive anything, the program halts. But it doesn´t. However in the real LAN I opened such programs as I wanted, and the transfer continues.

The laptop is a Toshiba CDT460 with a Pentium 166 Mhz processor, 96 Mgs Ram, and the pc is a PentiumIII 666 Mhz 256 Mgs Ram. To avoid the difference of speed I used semaphores in the program, so the pc does not send nothing if the laptop have not finished of receiving and gives the order of continuing. I have SuSE linux 7.3 installed in the laptop and Debian 3.0 in the pc, and the Perl version installed in both is 5.8, maybe it should be useful.

Well, thanks to all for read this bible, and excuse my english!