I'm not familiar with what Net::Telnet does internally, but the following old usenet post may help.... it involves taking the fileevent on the FILEDESCRIPTOR of the socket. The following shows the filedescriptor accessed by sysread, but fileno probably could be used.

    From: [1]Benjamin Goldberg ([2]goldbb2@earthlink.net)
   Subject: New FAQ idea.
   Newsgroups:
   [4]comp.lang.perl.misc
   Date: 2002-11-16 21:35:19 PST

One question that is frequently asked:

   Why does my IO deadlock, even though I'm using IO::Select or Tk::fi
+leevent?

You've probably got some code which does something like this:

   $MW->fileevent( $socket, 'readable', sub {
      my $line = <$socket>
        or $MW->fileevent( $socket, 'readable', ''), return;
      # process $line
   } );

Or like this:

   my $select = IO::Select->new($socket);
   while( () = $select->can_read($timeout) ) {
      my $line = <$socket> or last;
      # process $line
   }

The reason for the problem is that <> buffers data, but when IO::Selec
+t
and Tk::filehandle test for readability, they can only see the
underlying *unbuffered* filedescriptor, and the data that gets buffere
+d
confuses them.

The solution is to use the IO operator which works directly on the
underlying unbuffered filedescriptor (sysread), and do your buffering
yourself, in a seperate variable.  Be very careful that sysread is onl
+y
called *once* for each time that you've been told that a handle is
readable -- otherwise, it's quite possible that when the second call i
+s
made, no data will be there, and you'll get blocked.

Change your code to be like one of the following:

   my $buffer = "";
   $MW->fileevent( $socket, 'readable', sub {
      sysread( $socket, $buffer, 8192, length $buffer )
         or $MW->fileevent( $socket, 'readable', '' ), return;
      while( $buffer =~ s/^(.*\n)// ) {
         my $line = $1;
         # process $line
      }
   } );

Or like this:

   my $select = IO::Select->new($socket);
   my $buffer = "";
   while( () = $select->can_read($timeout) ) {
      sysread( $socket, $buffer, 8192, length $buffer )
        or last;
      while( $buffer =~ s/^(.*\n)// ) {
         my $line = $1;
         # process $line
      }
   }

It's important to be aware that one call to sysread can return less th
+an
one line, or it could return more than one line.  By using a while loo
+p
in this manner, both cases are dealt with equally well.
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