Solved

Telnet - disabling the echo

Posted on 2002-07-28
5
488 Views
Last Modified: 2010-04-21
Hi

I'm creating a Telnet like programm.
I want to know, how can I send data to the remote telnet (the telnet to connect to me), so a string will not echo (such as in password scanarios).
I can't find where in the RFC it's defined.

Can anyone help ?

Liron
0
Comment
Question by:lirong
5 Comments
 
LVL 51

Expert Comment

by:ahoffmann
ID: 7183769
man ioctl
man stty
0
 
LVL 14

Expert Comment

by:chris_calabrese
ID: 7185567
As for the RFC's, they're mum because it's not a protocol issue, but rather an issue for the host the server is running on (whether the OS thinks it should do character echo or not).
0
 

Expert Comment

by:skatethere
ID: 7267200
You've probably figured this out by now, but if not...

Most telnet client/servers negotiate two options that control the state of character echo: WILL ECHO and WILL SUPPRESS GO AHEAD.

These two settings specify that each character should be sent from the client to the server, echoed by the server, and displayed on the client when the echo is received.  This reverses what the original RFC854 says about all echos being local and all transmissions been line-at-a-time.

This is done in order to allow the server to control whether or not a character is echoed (and to improve interactivity).  With these settings in place, all a server needs to do to hide a password is to not echo it.

Practially speaking, if you are running a shell on your server to interact with the client, you would call 'stty -echo' to effect this change, and then 'stty echo' to reestablish echo.

In a program, look at the termio(7) ioctl(2).

  --kirby
0
 
LVL 21

Expert Comment

by:tfewster
ID: 7921715
No comment has been added lately, so it's time to clean up this Topic Area.
I will leave a recommendation for this question in the Cleanup topic area as follows:

- PAQ, no points refunded

Please leave any comments here within the next 7 days

PLEASE DO NOT ACCEPT THIS COMMENT AS AN ANSWER !

tfewster
Cleanup Volunteer
0
 

Accepted Solution

by:
SpideyMod earned 0 total points
ID: 7967308
0

Featured Post

Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
Hyper-threading config in Solaris 6 190
Sparc Solaris hangs without crash dump & no events from messages 3 92
UNIX SCP 5 87
SCP a file to multiple machines using a script 4 81
Attention: This article will no longer be maintained. If you have any questions, please feel free to mail me. jgh@FreeBSD.org Please see http://www.freebsd.org/doc/en_US.ISO8859-1/articles/freebsd-update-server/ for the updated article. It is avail…
Installing FreeBSD… FreeBSD is a darling of an operating system. The stability and usability make it a clear choice for servers and desktops (for the cunning). Savvy?  The Ports collection makes available every popular FOSS application and packag…
Learn how to get help with Linux/Unix bash shell commands. Use help to read help documents for built in bash shell commands.: Use man to interface with the online reference manuals for shell commands.: Use man to search man pages for unknown command…
Learn how to navigate the file tree with the shell. Use pwd to print the current working directory: Use ls to list a directory's contents: Use cd to change to a new directory: Use wildcards instead of typing out long directory names: Use ../ to move…

735 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question