Please Whitelist This Site?

I know everyone hates ads. But please understand that I am providing premium content for free that takes hundreds of hours of time to research and write. I don't want to go to a pay-only model like some sites, but when more and more people block ads, I end up working for free. And I have a family to support, just like you. :)

If you like The TCP/IP Guide, please consider the download version. It's priced very economically and you can read all of it in a convenient format without ads.

If you want to use this site for free, I'd be grateful if you could add the site to the whitelist for Adblock. To do so, just open the Adblock menu and select "Disable on". Or go to the Tools menu and select "Adblock Plus Preferences...". Then click "Add Filter..." at the bottom, and add this string: "@@||^$document". Then just click OK.

Thanks for your understanding!

Sincerely, Charles Kozierok
Author and Publisher, The TCP/IP Guide

NOTE: Using software to mass-download the site degrades the server and is prohibited.
If you want to read The TCP/IP Guide offline, please consider licensing it. Thank you.

The Book is Here... and Now On Sale!

Searchable, convenient, complete TCP/IP information.
The TCP/IP Guide

Custom Search

Table Of Contents  The TCP/IP Guide
 9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)
      9  TCP/IP Key Applications and Application Protocols
           9  TCP/IP Interactive and Remote Application Protocols
                9  Telnet Protocol

Previous Topic/Section
Telnet Connections and Client/Server Operation
Previous Page
Pages in Current Topic/Section
Next Page
Telnet Protocol Commands
Next Topic/Section

Telnet Communications Model and the Network Virtual Terminal (NVT)
(Page 3 of 4)

NVT ASCII Control Codes

Regular ASCII consists of 95 regular, “printable” characters (codes 32 through 126) and 33 control codes (0 through 31 and 127). The Telnet standard specifies that the output device must be able to handle all the printable characters, and it mandates how several of the other common ASCII control codes should be interpreted. Of these codes, three (0, 10 and 13) are required to be accepted by all Telnet software; five others are optional, but if supported, must be interpreted in a manner consistent with the Telnet specification. They are all described in Table 280.

Table 280: Interpretation of Standard Telnet NVT ASCII Control Codes

ASCII Value (Decimal)

Character Code

ASCII Character


Support Optional / Mandatory




No operation (no effect on output).





Produces an audible or visible signal on the output without moving the print head. This notification may be used to get the user’s attention, as in the case of an error.




Back Space

Moves the print position one character to the left.




Horizontal Tab

Moves the printer to the next horizontal tab stop. The standard does not specify how devices agree on tab stop positions; this can be negotiated using Telnet options.




Line Feed

Moves the printer to the next line, keeping the print position the same.




Vertical Tab

Moves the print line to the next vertical tab stop. As with the “HT” character, devices must use an option to come to an agreement on vertical tab stop positions.




Form Feed

Moves the printer to the top of the next page (or on a display, clears the screen and positions the cursor at the top.)




Carriage Return

Moves the printer to the left margin of the current print line.


Previous Topic/Section
Telnet Connections and Client/Server Operation
Previous Page
Pages in Current Topic/Section
Next Page
Telnet Protocol Commands
Next Topic/Section

If you find The TCP/IP Guide useful, please consider making a small Paypal donation to help the site, using one of the buttons below. You can also donate a custom amount using the far right button (not less than $1 please, or PayPal gets most/all of your money!) In lieu of a larger donation, you may wish to consider purchasing a download license of The TCP/IP Guide. Thanks for your support!
Donate $2
Donate $5
Donate $10
Donate $20
Donate $30
Donate: $

Home - Table Of Contents - Contact Us

The TCP/IP Guide (
Version 3.0 - Version Date: September 20, 2005

Copyright 2001-2005 Charles M. Kozierok. All Rights Reserved.
Not responsible for any loss resulting from the use of this site.