Dear Perl Monks:
I am trying to write a GUI tool in Perl/Tk. It's purpose is to drive equipment at work, which is a
digital cross connect system. I have have almost everything debugged and working in a simulation mode.
What I haven't yet figured out is the network communication part.

When I use the stock Microsoft Telnet program, the server responds properly, the response is immediate.
For both a "!" response to a CR, and for a command sent. Works properly.

When I use Perl's socket functions in my Client (use Net::Telnet on the Client) and (use Socket) on the server,
I have to send another "!" for the Client to show the data on the screen.

I figure that since the stock Telnet program works properly, it's not the server (use Socket).

My Client's local console gets updated the same time as the Tk text window.
(after ! is sent after a command is sent to the server).

In my program the Perk/Tk GUI... the link partially works. (1 for 1 with a ! sent),
but when I send a command an extra CR/! is needed for data to appear on the client side
(on both console and Tk windows). (Yes, I repeated myself, sorry... and I think I repeat below as well).
-------------------------------------------------------------------------------
Here are code samples. Client side, and this works... gets an immediate response. (which is a "!")

$t->print("!");
my $data = $t->get();
print STDOUT "$data\n";
WriteToScreen($data);
return;

[download]

-------------------------------------------------------------------------------
Client Side, and this does not work... I have to enter another ! (the above) to get a response.

print STDOUT "Get_CMap() Live Mode\n";
select($t);
$t->print($CMap_cmd);
$t->flush(); # this flushes the ouput buffer, but it is $|=1 anyway.
$newCMapData = $t->get();
print STDOUT "$newCMapData\n";
WriteToScreen($newCMapData);

[download]
-------------------------------------------------------------------------------
My program's write sub: (the scroll bar works ok, everything else works ok).
 sub WriteToScreen {
      my ($msg) = @_;

      $screen->insert("1.0", $msg);
      $numlines = ($screen->index("end")-1);
      $screen->configure(-state => "normal");
      if ($screen->index("end-1c") != "1.0") {
         $screen->insert_end("\n");
      }
      $screen->insert_end($msg);
      $screen->see("1.0");
      $screen->configure(-state => "disabled");
      $screen->yview("end");
}

[download]
-------------------------------------------------------------------------------
Data being sent by the server: (works with stock telnet, does not work with my program (as above):

$cm1 = "M 11:24:49 25,00 7 UTL QRY CMAP 064 TODC---- TYPE DC102 4 LN M
+SG:\r\n
 04124  20003  19317  19318  00000  19320  19324  19315\r\n
 19323  19314  19316  19319  00000  19601  00000  20103\r\n
 19604  07301  07302  07303  00403  07304  19407  19410   COMPL\r\n";

[download]

-------------------------------------------------------------------------------
This is the key routine in the server... sends the above data. 

  if ($cmd =~ m/cmap 111/ig) {
     select (NS);
     $|= 1;
     select (NS);
     print NS "$cm1";
     print NS "\n";
     print STDOUT "$cm1";
  }

[download]

This is the portion of the server that sends the ! in response to a !: 

    if ((length($ll) < 3) && ($ll !~ /!/g)) {
        print NS "!";
        print STDOUT "3!\r\n";
        next;
        }

[download]
This is my first post here. Sorry if it is not what is wanted. I don't get what I'm doing wrong. At the risk of repeating myself... When I send a ! I get a ! right back (my choice of a communication indicator). No delay, nothing further needed. When I send a command (in this case cmap 111), the data does not come back to the client until another ! is sent.

Any ideas on what might be causing this? I've got the buffers set hot ($|=1;) and I have a good pipe between the two endpoints (at this time it is just thru my local computer's stack... two different ports). The server script uses the Socket code. The Client uses Telnet code. Should I go to Socket code on the Client...? Are there incompatibilities between the two systems? I assume since Telnet works ok, the server code is ok. I realize that programming is not a spectator sport, and that I'm not really a programmer. But I'm trying. Have tried, and have worked this one over a lot before posting here. Thanks in advance for your help.

In reply to Telnet Client/Server: What am I doing wrong? by PM_Visitor

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