File Transfer ProtocolFile Transfer Protocolin in “Client Server “Client Server Computing” Computing”

BY

Mwendwa Kivuvakivuva@kenya.or.kewww.transworldafrica.com

16 Feb 2011

atCatholic University of Eastern

AfricaMain Campus, Nairobi, Kenya)

CONTENTSCONTENTS

IntroductionDesired OutcomesWhat is FTP?Modes of TransferBasic StepsBasic CommandsTransfer using GUI toolsWays to Connect to FTP ServersSummaryTerminology

INTRODUCTIONINTRODUCTION

The objectives of this FTP session are: 1) to demonstrate sharing of files, 2) to transfer data reliably and

efficiently,3) to explain different file viewing

software. 4) familiarize with terminology relating

to FTP5) help navigate in ftp directories6) Know the Basics of ftp

DESIRED OUTCOMESDESIRED OUTCOMES Use the FTP program. Recognize different types of file extensions. E.g.:

-.txt, .avi, .jpg. Know how to login as “anonymous” in FTP programs Know the difference between ASCII files and Binary

files. Know how to end an FTP session. Use basic FTP commands. Define FTP. Know that FTP is “case sensitive”. Connect to other FTP addresses and navigate in them. Know you will need to have an “Anti-virus” program

on your machine (**software on the net may have a virus).

WHAT IS FTP?WHAT IS FTP?FTP (RFC 959) works on the client/server

principle. A client program enables the user to interact with a server in order to access information and services on the server computer.

Files that can be transferred are stored on computers called FTP servers. To access these files, an FTP client program is used. This is an interface that allows the user to locate the file(s) to be transferred and initiate the transfer process.

FTP uses two TCP Ports ◦ one for control (port 21)◦ one for data transfers (port 20)

Goals of FTPGoals of FTPSharing of filesIndirect use of remote computersHandle different file systemsTransfer data reliably and

efficiently

MODE OF TRANSFERMODE OF TRANSFER

There are two modes of transfer in FTP: ascii and binary.

ASCII is used only for files saved in ASCII format (this includes Postcript files)

Binary is used for files that are formatted and saved using a wordprocessing software like WordPerfect (.txt), spreadsheets (.xls), images (.jpg, .gif), and many executable programs (.exe) and videos (.avi).

FTP clients select the transfer mode automatically.

Active Mode FTPActive Mode FTP Client connect from a random unprivileged port (n >

1023) to the servers command port (21) and sends port command to tell server to connect to n+1 then listens on the next higher unprivileged port (n+1) for server responses. The server connects from it’s data port (20) to the client data port (n+1)

ClientServer

20 21 1026 1027

1

2

3

4

Passive Mode FTPPassive Mode FTP Client opens two random unprivileged ports ( n >

1023 and n+1; ex 1026 and 1027) and connects the first port (n) to server command port 21 and issues a pasv command (server sends port to use for data); client connects to servers specified data port, server completes connection.

ClientServer

20 21 1026 1027

1

2

2024

3

4

Transfer Files in a Transfer Files in a Heterogeneous Host Heterogeneous Host EnvironmentEnvironment

Due to multiple hardware types and operating systems file are converted to four environmentally neutral data type for transport and the converted to local types at the destination◦ ASCII A NVT-ASCII◦ EBCDIC E EBCDIC Text◦ IMAGE I Raw binary, series of octets◦ LOCAL L Raw binary using a variable

byte sizeClient responsibility to tell server data type

to useDefault data type, unless otherwise

specified is ASCII

File StructuresFile StructuresOperating System store files in

different structuresFTP defined file structures for

transporting files◦ File F Unstructured, sequence of bytes◦ Record R Series of records◦ Page P Series of data blocks (pages)

Default file structure is File (F)File Structure specified using STRU

command

BASIC STEPS TO USE FTPBASIC STEPS TO USE FTP

Connect to the FTP serverNavigate the file structure to find

the file you wantTransfer the fileThe specifics of each step will

vary, depending on the client program being used and the type of Internet connection.

FTPFTP ModelModel

User User Interface

User PI

User DTP

Server PI

Server DTP

Local file system

Remote file system

Data Connection

Control connection

PI = Protocol InterpreterDTP = Data Transfer ProcessUser FTP

Server FTP

BASIC FTP BASIC FTP COMMANDSCOMMANDS

• FTP - initiate ftp session• open <host> - connect to an ftp server• binary - specify files to up/download; are

more than flat text (up files, images, programs, etc.)

• get <filename> - download a file from the server

• put <filename> - upload a file to the server

• close - close connection to the server• quit/exit - end the ftp session• user - re-enter login name

FTPFTP CommandsCommands• pwd - display present working directory

on server• lpwd - display the local present working

directory (on connecting machine)• cd - change directory• dir or ls - directory listing of

files/directories on Server• lcd - change directory on Local Machine• lcd~ - home shortcut• mget *.* - multiple file downloads• mput *.* - multiple file uploads• cdup - to move backwards to the previous

directory

Login using MSDOSLogin using MSDOS

Typical FTP RESPONSE Typical FTP RESPONSE Scenario Scenario

(Connect to FTP server)

220 Service Ready

USER username

331 User ok, password required

PASS password

230 User Logged in

RETR test.txt

150 Opening data connection

(Server makes data connection to local host)

226 Transfer complete

User FTP Server FTP

Copy file from serverCopy file from server Click on Start>Run >type CMD>Enter FTP Open kenya.or.ke Your login name Your password ftp>lcd c:\filename (this is the file you want

to download into. Specify location of local directory)

ftp> binary ftp>hash (you want it “on”) just type hash at

the prompt if its “off” ftp>dir c* - (yes, use an asterix) ftp>get <filename> The file is now in your local directory

USING GUI TOOLS for USING GUI TOOLS for FTPFTPFTP clients can be interactive

command-line based, or Graphical User Interface (GUI) clients for different operating systems.

Popular FREE and Open Source FTP GUI tools are Filezilla, cuteFTP and WinSCP.

Using WinSCPUsing WinSCPDownload winscp from

www.winscp.netOpen the winscp.exe programAdd your server detailsHostname: kenya.or.keUsername: anonymousPassword:Port Number: 21Protocol: FTPAfter Login, you get a File Manager

showing the Client computer, and the Server Computer

TRANSFER FILES USING TRANSFER FILES USING GUI (WinSCP)GUI (WinSCP)

WinSCP loginWinSCP login

Transfer of files using Transfer of files using WinSCPWinSCP

Select the source file and the destination location

Drag the source file to the destination folder

To delete a file, right click on it then click delete

To change permissions on a file, right click on the file, then select Properties. On the permission section, tick or untick Owner, Group or Other e.g. 777 means all permissions

Copying from client to Copying from client to serverserver

After CopyAfter Copy

Other Operations on Other Operations on WinSCPWinSCPCreate directoryList Directory ContentsDelete filesChange permissionsCompress and uncompress filesTransfer filesCopy and move files

CONNECT TO OTHER FTP CONNECT TO OTHER FTP SERVERSSERVERS

At your ftp> prompt simply type in their address. e.g. : ftp>cuea.edu

In Firefox, type the ftp address in the top box. e.g. : ftp://cuea.com

Login as “anonymous”, but be sure to give your complete e-mail address as the password.

Once you are at their ftp> prompt type “dir”. This will bring up their list of files for you to select from.

When you have chosen a file, at the ftp> prompt type - “cd pub” (or whatever) then type “dir” again.

Choose the particular file you want to download. Set transfer mode to binary. Make sure “hash” is “on”. ftp> get (filename) This will engage the transfer to your computer.

COMPRESSED FILESCOMPRESSED FILES

Sometimes you may come across files on FTP that are compressed.

Compression decreases the file size and enables more files to be stored on the server, and also makes file transfer times shorter.

To be able to use a compressed file it needs to be decompressed using compatible software.

Remember to keep an up-to-date version of virus checking software on your computer before you transfer files to it.

You can recognize a compressed file by its extension. Eg. .z, .gz, .sit, .zip.

Transfer these files in Binary Mode. Once they are on your machine you need special

software to decompress them. This software are often found free on the net..

Closing FTP SessionsClosing FTP Sessions

To Logout of an FTP program you must type EXIT at the ftp> prompt. When you type CLOSE it doesn’t exit out of the FTP program.

When done browsing files in a remote server type: ftp>close, you will still have ftp> on your screen since you didn’t “exit” the program. You can either type “exit” or the word “open” and another FTP address.

SUMMARYSUMMARY FTP (File Transfer Protocol) enables files to be

transferred from one computer to another. An FTP client program is an interface that allows the

user to locate file(s) to be transferred and initiate the process.

Through anonymous FTP, users have access to many different types of files including shareware, freeware, upgrades and documents.

You can transfer and view files that may aid you in writing proposals, or sending and receiving information to book vendors, and also can be used to electronically send a large document to another user without having to print it out and deliver them a hard copy.

Using FTP is a fun and sometimes challenging adventure. As new technology and equipment become more commonplace in our work environments, the means by which we learn and teach must evolve and change just as rapidly as the technology.

FTP TERMINOLOGYFTP TERMINOLOGY ASCII - American Standard Code for Information

Interchange) -- Standard for the code numbers used by computers to represent all the upper and lower-case Latin letters, numbers, punctuation, tec. There are 128 standard ASCII codes each of which can be represented by a 7 digit binary number: 0000000 through 1111111.

BINARY - Used for files that are formatted and saved using a wordprocessing software like WordPerfect, spreadsheets, images, and many executable programs.

BROWSER - A program which allows a person to read hypertext. The browser gives some means of viewing the contents of nodes, and of navigating from one node to another.

FTP - (File Transfer Protocol)-a client program that enables the user to send files from one computer to another via the telephone network with the aid of the internet.

LOCAL PC - your desktop computer that you will transfer files to.

HOST - Any computer on a network that is a repository for services available to other computers on the network..

LOGIN - The account name used to gain access to a computer system, or the act of entering into a computer system.

FTP TERMINOLOGYFTP TERMINOLOGY(CONT.)(CONT.)

NODE - Any single computer connected to a network. PROTOCOLS - sets of communication rules that allow clients and

servers to communicate accurately with each other. SERVER - A computer, or a software package, that provides a

specific kind of service to client software running on other computers.

INTERNET - The vast collection of inter-connected networks that all use the TCP/IP protocols and that evolved from the ARPANET of the late 60’s and 70’s.

TCP/IP - Transmission Control Protocl/Internet Protocol -- /tus us te syute if oriticiks that defines the Internet. To be truly on the Internet, your computer must have TCP/IP software.

ANONYMOUS FTP - Allows a user to retrieve documents, files, programs, and other archived data from anywhere in the Internet without having to establish a userid and password. By using the special userid of “anonymous” the network user will bypass local security checks and will have access to publicly accessible files on the remote system.

ARCHIVE SITE - A machine that provides access to a collection of files across the Internet.

USER ID - On most host systems, the first time you connect you are asked to supply a one-word user name. This can be any combination of letters and numbers. This is usally also your e-mail name.

FTP TERMINOLOGYFTP TERMINOLOGY(CONT.)(CONT.)

VIRUS PROGRAMS -viruses are small, invasive programs that are designed to create havoc within your computer systems. There is software to protect your computer from viruses. If you plan to swap disks with others, the first software program you should install should be a virus protection program.

TELNET - The command and program used to login from one Internet site to another. The telnet command/program gets you to the “login” prompt of another host.

CLIENT - A software program that is used to contact and obtain data from a Server software program on another computer, often across a great distance. Each Client program is designed to work with one or more specific kinds of Server programs, and each Server requires a specific kind of Client.

VIRUS - A program which replicates itself on computer systems by incorporating itself into other programs which are shared among computer systems.

FTP TIPSFTP TIPS

When retrieving non-text files, you must use Binary Mode, otherwise the file(s) get messed up.

FTP is case sensitive) Be aware that software files on the net may

have a virus.

ENDEND