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using interact with TCP socket
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Phil Freed  
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 More options May 26 2005, 3:08 pm
Newsgroups: comp.lang.tcl
From: "Phil Freed" <clt...@freed.com>
Date: Thu, 26 May 2005 19:08:43 GMT
Local: Thurs, May 26 2005 3:08 pm
Subject: using interact with TCP socket
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Platform:  WinXP, cygwin

I have wrote a simple converter in Expect that is designed to take in a
telnet connection and pass it through to an SSH connection.

basically, the code is simple:

socket -server Server -myaddr 127.0.0.1 5555
vwait forever

And the Server routine (simplified to remove error checks and the like) is:

proc Server {channel clientAddr clientPort} {
  spawn -open $channel
  set telnet $spawn_id

  spawn  "/usr/bin/ssh" u...@domain.com
  interact -u $telnet

}

This works fine, except that anything typed into my telnet session appears
on the screen twice.  I've tried everything I can think of -- changing the
spawns to noecho, nottyinit & nottycopy, etc.  Is this an artifact of
opening a TCP connection with "spawn -open"?  Is there something simple that
I'm missing?  Is it simply the platform that I'm on?

Thanks for any light you may be able to shed on this.


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Don Libes  
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 More options May 31 2005, 5:02 pm
Newsgroups: comp.lang.tcl
From: Don Libes <li...@nist.gov>
Date: 31 May 2005 17:02:55 -0400
Local: Tues, May 31 2005 5:02 pm
Subject: Re: using interact with TCP socket
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If I understand your scenario (very cute by the way!), the extra echo
is being generated by your telnet client itself.  You didn't show you
are using a telnet client in the scenario but I assume that's what
you're using, yes?  The telnet client has a property of echoing by
default if used to any non-telnetd port.

Off the top of my head, I forget the option to turn off echoing, but
you can find it in any telnet documentation.  However, telnet also
uses a very crude line mode (which is why echoing is kinda important).
Depending on your requirements, you might want to deal with that too.

Don


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Michael A. Cleverly  
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 More options Jun 8 2005, 1:25 am
Newsgroups: comp.lang.tcl
From: "Michael A. Cleverly" <mich...@cleverly.com>
Date: Tue, 7 Jun 2005 23:25:15 -0600
Local: Wed, Jun 8 2005 1:25 am
Subject: Re: using interact with TCP socket
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On Tue, 31 May 2005, Don Libes wrote:
> "Phil Freed" <clt...@freed.com> writes:
>> This works fine, except that anything typed into my telnet session appears
>> on the screen twice.  I've tried everything I can think of -- changing the
>> spawns to noecho, nottyinit & nottycopy, etc.  Is this an artifact of
>> opening a TCP connection with "spawn -open"?  Is there something simple that
>> I'm missing?  Is it simply the platform that I'm on?
> Off the top of my head, I forget the option to turn off echoing, but
> you can find it in any telnet documentation.  However, telnet also
> uses a very crude line mode (which is why echoing is kinda important).
> Depending on your requirements, you might want to deal with that too.

The OP could try doing a:

     puts [format %c%c%c 255 251 1]

to output the escape code to tell (a proper) telnet client to turn off
echo.  For reference, you could (request to) turn it back on with:

     puts [format %c%c%c 255 252 1]

Michael


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