Internet and web world world wide web

FTP
Sunday, December 14, 2008

I hope that you are having as much fun participating in this workshop as I am having teaching it! :)

In the last lesson we used a tool called "Telnet" which allowed us to access remote computers and run programs on those remote computers.

In the next few lessons we are going to use a tool called "File Transfer Protocol" (or "FTP") which will allow us to access remote computers and retrieve files from these computers. Actually, it is probably more accurate to say that we will be using "anonymous" FTP, but I'll explain that in a minute.

What sort of files are available through FTP? Well, "hundreds of systems connected to the Internet have file libraries, or archives, accessible to the public. Much of this consists of free or low-cost {computer} programs for virtually every make of computer. If you want a different communications program for your IBM, or feel like playing a new game on your Amiga, you'll {probably} be able to get it {using FTP}."

"But there are also libraries of documents as well. If you want a copy of a recent U.S. Supreme Court decision, you can {get a copy using FTP}. Copies of historical documents, from the Magna Carta to the Declaration of Independence are also yours for the asking ... You can also find song lyrics, poems, {and} even summaries of every {Animaniacs} episode ever made. You can also find extensive files detailing everything you could possibly want to know about the Net itself". (1)

Before we get too in-depth into FTP, I think that now is as good a time as any to quickly review the client/server relationship that I briefly mentioned in lesson three (MAP03: Levels of Internet Connectivity).

"Client" is just another word for a program running on your service provider's system that enables you to talk to, and get stuff from, distant computers. The client on your service provider's system takes your commands and turns them into requests for information from programs -- "servers" -- running on other, distant computers.

The client/server relationship allows you to TELNET into remote computers and run programs on those remote computers, and it also allows you to use FTP to get files from remote sites.

The client/server relationship is also what makes my job as an Internet trainer quite difficult. While all of the FTP clients out there do the exact same thing, they all use different commands to do it.

Fortunately, if you can understand the basics of what happens during an FTP session, the commands -- no matter what client you are using -- are pretty easy.

The basic steps in an FTP session are:

1. Start-up your FTP client.
2. Give your FTP client an address to connect to (and, just like TELNET, step one and two can be combined into one easy step).
3. Identify yourself to the remote site.
4. Give the remote site your password.
5. Look around the directory for files.
6. Change Directories.
7. Set the transfer mode (optional).
8. Get the file(s) you want.
9. Quit.

Before I do that, though, there are three things that I need to emphasize:

1. FTP requires a heck of a lot of resources, both on your system and on the remote system that you are accessing. Because of this, FTP sessions should only be run during non-working hours (usually 6 PM to 6 AM local).

   I realize that this constraint is going to be a difficult for those of you who are reading this at work, and who only have Internet (and FTP access) through your employer. However, as responsible Internet citizens we have to remember that the FTP sites are providing us FTP access out of the kindness of their hearts. If we take advantage of this kindness, and access various FTP sites during working hours, those FTP sites may decide to close their doors to the public ... and then EVERYONE loses.
   
   

2. In light of what was said in #1, please do not flood SURAnet. In MAP15: FTPMAIL I will post a list of FTP sites that you can visit (much like the TELNET list I posted in MAP12: Telnet (Part Two)). Until I post that list, just sit back and enjoy the show :)
   
   
3. Since this lesson is already over 100 lines long, I hope that you won't mind if I break this FTP lesson into two lessons. The first lesson is in this document, and I'll finish it in the next document. This will mean that we will end this lesson in the middle of our sample FTP session, but it will also mean that this lesson won't be the size of a small book :)

ftp

>From there, you would give the client an FTP address to connect to.

Like TELNET, however, there is a way to combine these two steps into one, easy step. For most of you, to access your FTP client and give your client an address to hook up to, all you would have to do it type the command

ftp

   ftp ftp.sura.net
  Connecting to ftp.sura.net 128.167.254.179, port 21
  220 nic.sura.net FTP server (Version wu-2.4(1) Fri May 20 10:20:58
  EDT 1994) ready.
  USER (identify yourself to the host):

   >>>USER anonymous
  331 Guest login ok, send your complete e-mail address as password.
  Password:

   >>>PASS ********
  230-    SURAnet ftp server running wuarchive experimental ftpd
  230-
  230-Welcome to the SURAnet ftp server.  If you have any problems with
  230-the server please mail the to systems@sura.net. If you do have problems,
  230-please try using a dash (-) as the first character of your password
  230- -- this will turn off the continuation messages that may be confusing
  230-your ftp client.
  ...
  230 Guest login ok, access restrictions apply.
  Command: