Possibility 1: open 1 rtk_connection per accepted connection. That is, do the follow in the child after the fork:

$rtk_connection= IO::Socket::INET->new('PeerAddr'=>$rtk_ip, 'PeerPort'
+ =>$rtk_port, 'Reuse'=>1, 'Proto'=>'tcp') || warn "Can not create rtk
+ socket on IP $rtk_ip and port $rtk_port: $!\n";
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Of course, whether you can do that depends on what application you're connecting to on port 4004.

Possibility 2: Instead of forking, use select to be able to read from any open socket. See IO::Select for a sketchy example.