The <> operation (thus, readline($socket)) waits for the contents of $/ variable to appear on the socket before returning. Are you sure that remote host sends data containing it after someone connects to it?

Try setting your socket into non-blocking mode by adding Blocking => 0 to the constructor arguments. More useful information on non-blocking I/O can be found at http://www.kegel.com/dkftpbench/nonblocking.html and in perlfaq8.