If you are adding your client sockets to the IO::Select object, then when you call can_read, it will return an array of all the socket filehandles that are ready for reading, so when you call for my $fh ($sel->can_read()) { ... }, each time through the loop, $fh will contain the filehandle for a different client connection. The hash you created with all the descriptors is unnecessarry, the IO::Select object holds them for you.