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 tcpipguide.com". Or go to the Tools menu and select "Adblock Plus Preferences...". Then click "Add Filter..." at the bottom, and add this string: "@@||tcpipguide.com^$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.
|
|
|
|
FTP Internal Protocol Commands and Command Groups
(Page 1 of 2)
An FTP session begins with the establishment
of a TCP connection from an FTP client (user device) to an FTP server.
Once established, the control
channel is logically in place between
the Server-PI and the User-PI. All communication to manage the operation
of the protocol takes place over this channel. The User-PI sends protocol
commands to the Server-PI, which processes them and takes appropriate
action. The Server-PI responds back with reply codes to tell
the User-PI the result of the commands it issued and convey other important
information.
FTP Command Groups
Each command is identified by a short
three-letter or four-letter command code for convenience, and
performs a specific task in the overall functionality of FTP. There
are several dozen of these protocol commands, and to help organize them,
the FTP standard categorizes them into three groups, based on overall
function type:
- Access Control Commands: Commands that
are part of the user
login and authentication process, are
used for resource access, or are part of general session control.
- Transfer Parameter Commands: Commands
that specify parameters for how data transfers should occur. For example,
commands in this group specify the data
type of a file to be sent, indicate whether
passive
or active data connections will be used,
and so forth.
- FTP Service Commands: This is the largest
group, containing all the commands that actually perform file operations,
such as sending and receiving files. Commands to implement support functions,
such as deleting or renaming files, are also here.
Interestingly, the actual transmission
of FTP commands over the control channel is done using specifications
based on the Telnet protocol.
You may recall from the FTP
overview that Telnet and FTP are two of
the very oldest TCP/IP applications, the former being for direct
network use and the latter for indirect resource access.
They were developed at around the same time, and setting up the FTP
control channel to act as a type of Telnet connection is a good example
of how Internet standards try not to reinvent the wheel.
Key Concept: FTP operation is controlled through the issuing of protocol commands from the FTP client to the FTP server. Each command has a three- or four-letter command code that indicates its function. The commands are organized into three groups: access control commands used for login and general session control; transfer parameter commands that control how transfers are performed; and FTP service commands, which are used to perform actual file operations. |
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! |
|
|
Home -
Table Of Contents - Contact Us
The TCP/IP Guide (http://www.TCPIPGuide.com)
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.
|