$user = <$client_socket>;
 chop($user); #remove the \n
 print "$prefix USER = $user\n";
  unless (open (USERNAME, "username")) 
	 {
       print "ERROR:Cannot open username file.\n";
       exit(1); # ERROR
      }
	while(<USERNAME>)
		{
		my @newusername = <USERNAME>;
	foreach $name (@newusername)
		{
       if($name ne $user) {
	   print $client_socket "ERR\n";
       print "$prefix ERROR: user $user not permitted to use this mode.  Exiting.\n";
       close(USERNAME);
	   exit(1);
	 	     }
		}
		}
     #else, continue
     print $client_socket "ACK\n";  # approve the user.  Limit this in the future.
	 close(USERNAME);