FTP File Transfer Protocol

1
FTP File Transfer Protocol

• FTP - File Transfer Protocol is one of the
  original Internet services. It was designed to
  move files from one computer to another
• Today people use a variety of technologies to
  move files between machines including
• email attachments, web browsers, LAN based file
  sharing, peer-to-peer file sharing, or
  proprietary file sharing clients
• FTP is based on the client/server model where
  there is an FTP client (that may be standalone or
  the client may be in a web browser), a protocol,
  and a server.

2
How FTP Typically Works

• The user runs an FTP client on their local
  machine
• They tell their client to opens a session with an
  FTP server on a remote machine
• The user logs onto the remote machine
• The user lists the files at the remote machine
  and moves into the right directory on both the
  local and the remote machine
• The user indicates if the file to transfer is
  binary or ascii, then puts files to the remote
  machine, or gets files from the remote machine
• The user closes the session

3
FTP Clients

• Historically the first clients were command
  based. i.e. on Unix or at a DOS command prompt
  type
• ftp or ftp host.domain
• Commands are Unix like (cd, mkdir to traverse the
  folder hierarchies, put and get to move
  files) and it can be difficult or confusing for a
  novice user

4
FTP Graphical Clients

• Today we have GUI FTP clients to make it a little
  easier to use.
• On Windows popular clients are WS-FTP or
  CuteFTP.
• On Mac Fetch. Many more available, some
  commercial some free
• FTP client functionality is also built into most
  Web browsers today. Enter an address like ftp//
  to get to an FTP site or often you can download
  using http
• Since some firewalls may block FTP, http based
  downloads have yet another advantage for some
  users
• Some applications let you save directly to an FTP
  site, i.e.. In Word you can do a File/Save As and
  enter and address like ftp//host.domain/filename
  to save on some remote FTP servers

5
FTP the big problem

• Same as telnet the protocol sends data in clear
  text.
• As a result, a packet sniffers could potentially
  intercept user passwords which makes standard FTP
  a security threat.
• Many organizations (including CAC at UW) have
  disabled FTP as a result and use other file
  transfer technologies instead.
• Since other technologies are available and a
  little easier to use FTP is not as popular as it
  once was. Many sites that make software
  available today for instance do it via a Web
  front end, not by making an FTP site available.
  
• But FTP still widely used, especially for more
  specialized applications when you want to limit
  the download access to just certain people

6
Important Details.

• Generally speaking when you do file transfers
  with most you want to be sure to specify if the
  file is ascii or binary
• What if we have a text file and tell it to be
  sent in binary? Unfortunately text isnt exactly
  the same on all systems - Unix and PCs have
  different line endings. ltCRgt vs. ltCRgtltLFgt. So it
  is important to say you are sending text if that
  is what it is
• Also remember that case counts on some operating
  systems and there can be complications if you
  have used punctuation and or spaces in file names

7
Command Mode FTP

• WS-FTP and other GUIs like SSH FTP make the
  FTP process very simple. Unfortunately you dont
  always have access to a GUI - often all you may
  have is a command mode client.
• This is the case when you use Unix and the Dante
  command prompt .
• Also, Win95/98/XP include a basic command line
  FTP client when you setup TCP/IP on your PC, do a
  Start, Run, and type FTP to use it

8
FTP Command-Line Overview

• Run FTP client (on Windows Start/Run, FTP) at FTP
  prompt type
• help - to see list of commands available
• open host.domain - to connect to the remote host
• Username xxxxxx
• Password
• ls, cd, pwd - to manipulate the remote
  filesystem
• lcd - manipulate local filesystem
• binary or bin - to tell FTP you are transferring
  a binary file
• hash - to tell FTP you want to see progress with
  hash marks ( signs are displayed as the file is
  copied)
• get filename - to get a file from the remote
  computer
• put filename - to put a file on the remote
  computer
• ! To temporarily go to a command prompt, exit to
  come back

9
Step 1 Initiate the connection

• Start your command mode FTP client
• In Windows do
• Start, Run, FTP
• You will receive the FTPgt prompt
• Type the command open machine name
• e.g. open ischool.washington.edu
• On Unix type ftp and again you will receive the
  FTPgt Prompt

10
Step 2 - Login

• Login required for security, FTP will prompt for
  your userid and password
• Can see then you can only FTP to and from sites
  where you are defined as a user
• The exception is using something called
  anonymous FTP
• So...login with either a userid or as anonymous
• FTP will put you in a default directory on the
  remote machine
• Use ls or ls l to see a list of files there

11
Step 3 Move to the right place

• Use the cd command to change directories on the
  remote machine until you get to the right place
• Example cd downloads
• Use the lcd (local change directory) command to
  change to the right directory on your computer
• Example lcd C\My Documents

12
How do you know where to go?

• Often times you may be told by someone that the
  file you need is in a certain location
• Other times you may be browsing the site and not
  even know what is available
• If browsing you can look for several common file
  names to help you see what is there
• index, index.txt, readme, LS -LR, are good
  possibilities
• Also many sites have a pub directory which is
  where they store their public files. Try
  cd-ing to the pub directory and look for files
  like those above

13
Step 4 Indicate the file type

• Is the file a binary file or is it a text file?
• By default FTP assumes files are text files
• If it is binary (a graphic, a sound, a Word
  document) you need to specify that
• At the FTP prompt type
• bin

14
Step 5 Initiate the transfer

• Use one of
• Put--- Move file from client to the server
• Get--- Move file from server to client
• Very important not to get confused and overwrite
  an existing file.
• So are you the client or are you the server?
• Where you running this FTP program from is key

Client Machine
Server Machine
15
FTP Commands for Moving Multiple Files

• prompt ---gt turns off prompt on each file
• mget ----gt Get all files in the directory
• mput ----gt Put all files in the directory
• These commands are limited
• Do not handle subdirectories
• For bundling up multiple directories into a
  single file, archiving tools are used first

16
Sample FTP Session

• C\gtftp ftp.microsoft.com
• Connected to ftp.microsoft.com.
• 220 Microsoft FTP Service
• User (ftp.microsoft.com(none)) anonymous
• 331 Anonymous access allowed, send identity
  (e-mail name) as password.
• Password
• 230-This is FTP.Microsoft.Com.
• 230 Anonymous user logged in.
• ftpgt ls
• The listing of files and folders appears, removed
  from this sample to save space, found a folder
  and file I wanted
• ftpgt cd deskapps
• 250 CWD command successful.
• ftpgt bin
• 200 Type set to I.
• ftpgt lcd "D\My Documents"
• Local directory now D\My Documents.
• ftpgt get MSBGOLD.EXE
• 200 PORT command successful.
• 150 Opening BINARY mode data connection for
  MSBGOLD.EXE(1983683 bytes).

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Command Mode FTP Conclusion

• Depending on what environment you use, you may
  use it rarely or you may not have any option
• Not really that hard, uses the same basic
  commands that we may already know from Unix with
  the addition of put and get